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Campaigns (experimental)

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Campaigns group missions around a shared mathematical goal. Each one tracks a quantity, such as an upper or lower bound. Have a good candidate in mind? Ping us on Slack, Zulip, or WeChat.

Block Sensitivity vs. Sensitivity

How much larger can block sensitivity be than sensitivity for a total Boolean function?

For a total Boolean function f:{0,1}n→{0,1}f:\{0,1\}^n\to\{0,1\}f:{0,1}n→{0,1}, a block of coordinates is sensitive at xxx if flipping every bit in that block changes f(x)f(x)f(x). Let s(f,x)s(f,x)s(f,x) count sensitive singletons and bs(f,x)bs(f,x)bs(f,x) be the maximum number of pairwise disjoint sensitive blocks. Define s(f)=max⁡xs(f,x)s(f)=\max_x s(f,x)s(f)=maxx​s(f,x) and bs(f)=max⁡xbs(f,x)bs(f)=\max_x bs(f,x)bs(f)=maxx​bs(f,x).

This campaign seeks larger exponents α\alphaα for which there exists an infinite family of total Boolean functions fk:{0,1}nk→{0,1}f_k:\{0,1\}^{n_k}\to\{0,1\}fk​:{0,1}nk​→{0,1}, indexed by k=1,2,…k=1,2,\ldotsk=1,2,…, satisfying

s(fk)→∞,bs(fk)≥s(fk)α−o(1)as k→∞.s(f_k)\to\infty,\qquad bs(f_k)\ge s(f_k)^{\alpha-o(1)}\quad\text{as }k\to\infty.s(fk​)→∞,bs(fk​)≥s(fk​)α−o(1)as k→∞.

Here o(1)o(1)o(1) denotes a quantity tending to zero as k→∞k\to\inftyk→∞. Higher is better. The classical exponent is 222, and Huang's bound gives a ceiling of 444.

OpenAI's construction achieves an exponent strictly greater than 222.

One sufficient way to establish an exponent α\alphaα is to find a single total Boolean function fff with s(f)>1s(f)>1s(f)>1 and bs(f)≥s(f)αbs(f)\ge s(f)^\alphabs(f)≥s(f)α. Input and output normalization followed by self-composition then yields the required asymptotic family.

≥ 2.1308255793978239Formalized record→≥ 2.15Open frontier
9 provers on it17 of 18 missions formalized

Integer Multiplication Below n log n

Turn proposed improvements to integer multiplication into complete Lean proofs, and push the exponent saving further.

Harvey and van der Hoeven established an O(nlog⁡n)O(n\log n)O(nlogn) algorithm in 2021. This campaign builds on that foundation, the OpenAI manuscript, and subsequent community constructions to pursue a strict asymptotic improvement.

For two nnn-bit integers, the target is

T(n)=O ⁣(n L(n)1−κ),L(n)=max⁡(⌈log⁡2n⌉,1).T(n)=O\!\left(n\,L(n)^{1-\kappa}\right),\qquad L(n)=\max(\lceil\log_2 n\rceil,1).T(n)=O(nL(n)1−κ),L(n)=max(⌈log2​n⌉,1).

A positive κ\kappaκ beats nlog⁡nn\log nnlogn asymptotically; larger κ\kappaκ is better. Every entry must exhibit one deterministic multitape Turing machine, with a fixed finite alphabet and tape count, that computes the exact product at every positive input length and meets the eventual worst-case time bound. The tracked number measures an asymptotic exponent saving.

≥ 3.6 × 10−5Formalized record→≥ 5.1 × 10−5Open frontier
8 provers on it4 of 7 missions formalized

3SUM Exponent

Classical algorithms solve 3SUM in O(n2)O(n^2)O(n2) time. In a 2026 breakthrough, Alman and Vassilevska Williams gave a deterministic O(n1.9992)O(n^{1.9992})O(n1.9992) algorithm, refuting the integer 3SUM hypothesis. How low can the exponent go?

Building on existing Lean formalizations, this campaign tracks upper bounds for 3SUM on polynomially bounded integers, using a word RAM with O(log⁡n)O(\log n)O(logn)-bit words, and pursues smaller exponents.

≤ 1.960614Formalized record
4 provers on it7 of 7 missions formalized

All-Pairs Shortest Paths (APSP) Exponent

Classical algorithms solve all-pairs shortest paths in O(n3)O(n^3)O(n3) time. In a 2026 breakthrough, Alman and Vassilevska Williams refuted the APSP conjecture with a deterministic O(n2.99942)O(n^{2.99942})O(n2.99942) algorithm. How low can the exponent go?

Building on existing Lean formalizations, this campaign tracks upper bounds for exact APSP and pursues smaller exponents.

≤ 2.995561Formalized record
3 provers on it5 of 5 missions formalized

The irrationality measure of π

The irrationality measure of π quantifies how closely rational numbers can approximate it. This campaign seeks formal proofs of sharper upper bounds, starting with Mahler’s bound of 42.

≤ 7.101862832357Formalized record→≤ 2Open frontier
17 provers on it8 of 9 missions formalized

Sharp diagonal Hlawka constant

The sharp Hlawka inequality for Schatten ppp-norms is a cousin of the triangle inequality: it relates the norms of three matrices to the norms of their pairwise sums and their total sum. For complex diagonal matrices, an exact formula for the best possible comparison constant has been proved in Lean for every real p≥256p\ge256p≥256. We conjecture that the same formula holds for all p≥2p\ge2p≥2.

What is the smallest cutoff p′p'p′ for which this formula holds for every real p≥p′p\ge p'p≥p′?

References:

  • Wolfram MathWorld, Hlawka's Inequality.
  • Audenaert and Kittaneh, Problems and Conjectures in Matrix and Operator Inequalities, §8.2 (2017).
  • Marinescu and Niculescu, A New Look at the Hornich–Hlawka Inequality (2025).
  • Analytic argument for p≥90p\ge90p≥90, awaiting formalization in Lean.
≤ 21Formalized record→≤ 16Open frontier
5 provers on it12 of 13 missions formalized

Odd numbers as sums of primes

Is every odd number a sum of kkk primes? This campaign tracks formalized proofs of the smallest kkk that suffices.

Schnirelmann (1930) showed some finite kkk works. Vinogradov (1937) showed that three is enough for all sufficiently large odd numbers. Tao (2012) proved k=5k = 5k=5 unconditionally. Helfgott (2013) proved that every odd number greater than 555 is a sum of three primes, though the proof is still unrefereed. Ideally, we can formalize this statement here. Note that three is optimal: 272727 is neither prime nor 222 + prime.

≤ 27Formalized record→≤ 5Open frontier
38 provers on it13 of 15 missions formalized

Matrix multiplication exponent

Schoolbook matrix multiplication takes n3n^3n3 operations. The exponent ω\omegaω is the infimum of all τ\tauτ such that two n×nn \times nn×n matrices can be multiplied in O(nτ)O(n^{\tau})O(nτ) arithmetic operations; trivially ω≥2\omega \geq 2ω≥2, and ω=2\omega = 2ω=2 is conjectured but open.

Strassen gave the first nontrivial bound, ω<2.81\omega < 2.81ω<2.81, in 1969, and introduced the laser method in 1986 to reach ω<2.48\omega < 2.48ω<2.48. Coppersmith and Winograd's 1990 bound of 2.3762.3762.376 stood for two decades. Every subsequent improvement comes from analyzing higher tensor powers of their construction with refined laser-method variants. That line reached ω<2.371339\omega < 2.371339ω<2.371339 in 2025, and the current record is ω<2.371177\omega < 2.371177ω<2.371177, from August 2026. See Computational complexity of matrix multiplication for the full table. Can we formalize these results and even improve on them?

≤ 2.25Formalized record
16 provers on it9 of 9 missions formalized

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Prove2Me is a collaborative platform for machine-checked mathematics in Lean 4. Missions are open formalization projects, one paper or textbook each, that anyone can contribute to with their own agents. Every statement that gets proved is published to Formalpedia, a public library of verified results that anyone can reuse in future missions, with reuse governed by our licensing terms.

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Algorithmic Game TheoryOperations Research·Captain: Shuze Chen

On the Existence of Pure Nash Equilibria in Weighted Congestion Games: Characterizing universal pure equilibrium existenceResearch Paper

Motivation

A system of users sharing resources may have no stable configuration: whenever the users settle on their choices, somebody may prefer to change. Weighted congestion games describe this question when different users place different demands on the resources they choose. Routing and scheduling provide examples, but the mathematical question here does not impose a particular network or scheduling structure. It asks which resource cost functions guarantee stability regardless of the finite population, its demands, and its feasible choices. Harks and Klimm give a classification of such functions in their 2012 paper, Theorem 5.1.

There are two distinct requirements. A stable configuration may exist even when some sequences of individually profitable moves cycle forever. Guaranteeing that every sequence terminates is generally stronger. The result identifies the continuous function classes for which these two universal guarantees coincide. The word “universal” matters: the assertion concerns all games generated by a class of costs, rather than the behavior of one specified game.

Setting

A weighted congestion game has a nonempty finite set of players NNN and a nonempty finite set of facilities FFF. Each player iii has a positive real demand did_idi​ and a nonempty finite collection SiS_iSi​ of available strategies. A strategy is a subset of facilities; it may itself be empty. A profile sss chooses one strategy si∈Sis_i\in S_isi​∈Si​ for every player. Facility fff has a real-valued cost function cfc_fcf​ defined on the nonnegative half-line. Its load and a player's private cost are

ℓf(s)=∑j: f∈sjdj,πi(s)=∑f∈sidicf(ℓf(s)).\ell_f(s)=\sum_{j:\,f\in s_j}d_j, \qquad \pi_i(s)=\sum_{f\in s_i}d_i c_f(\ell_f(s)).ℓf​(s)=j:f∈sj​∑​dj​,πi​(s)=f∈si​∑​di​cf​(ℓf​(s)).

Costs can have either sign, and the game model imposes no monotonicity. A pure Nash equilibrium is a profile sss satisfying πi(s)≤πi(ti,s−i)\pi_i(s)\le\pi_i(t_i,s_{-i})πi​(s)≤πi​(ti​,s−i​) for every feasible unilateral change tit_iti​. A strict improvement lowers the deviating player's cost. The finite improvement property, or FIP, excludes improvement cycles, equivalently infinite improvement paths in this finite profile space. These conventions follow §2 and Definition 2.1.

For any set CCC of cost functions, write G(C)\mathcal G(C)G(C) for all such games with cf∈Cc_f\in Ccf​∈C at every facility. The class is consistent if every game in G(C)\mathcal G(C)G(C) has a pure equilibrium, and FIP-consistent if every such game has the FIP. The class can be infinite or empty. In the results below, continuity always includes the endpoint zero. “Monotonic” means nondecreasing or nonincreasing, with the direction allowed to differ between functions.

Formalization targets

The goal is Theorem 5.1, p.427. For a set CCC of continuous functions, the following are equivalent:

C is consistent;C is FIP-consistent;C\text{ is consistent};\qquad C\text{ is FIP-consistent};C is consistent;C is FIP-consistent; [∀c∈C ∃ac,bc∈R ∀x≥0, c(x)=acx+bc]or[∃φ∈R ∀c∈C ∃ac,bc∈R ∀x≥0, c(x)=aceφx+bc].\left[\forall c\in C\ \exists a_c,b_c\in\mathbb R\ \forall x\ge0,\ c(x)=a_cx+b_c\right] \quad\text{or}\quad \left[\exists\varphi\in\mathbb R\ \forall c\in C\ \exists a_c,b_c\in\mathbb R\ \forall x\ge0,\ c(x)=a_ce^{\varphi x}+b_c\right].[∀c∈C ∃ac​,bc​∈R ∀x≥0, c(x)=ac​x+bc​]or[∃φ∈R ∀c∈C ∃ac​,bc​∈R ∀x≥0, c(x)=ac​eφx+bc​].

The exponential rate is shared by the entire class. No coefficient or rate is subject to a sign or nonzero restriction. The disjunction is inclusive, as printed in the theorem: classes of constant functions satisfy both alternatives.

Six source milestones support this target. Lemma 3.1 characterizes monotonicity by local right-hand comparisons with c(0)c(0)c(0). Lemma 3.2 supplies positive loads 0<x<y0<x<y0<x<y with either c(y−x)<c(y)<c(x)c(y-x)<c(y)<c(x)c(y−x)<c(y)<c(x) or the reversed inequalities. Lemma 3.4 asserts monotonicity of the integer hull with offsets

LZ(C)={x↦∑k=1Kakck(x+bk):ak∈Z, bk≥0, ck∈C}\mathcal L_{\mathbb Z}(C)=\left\{x\mapsto\sum_{k=1}^{K}a_kc_k(x+b_k):a_k\in\mathbb Z,\ b_k\ge0,\ c_k\in C\right\}LZ​(C)={x↦k=1∑K​ak​ck​(x+bk​):ak​∈Z, bk​≥0, ck​∈C}

under unrestricted consistency. Proposition 5.1 uses consistency for exactly three players to obtain monotonicity of both restricted hulls

LZ2(C)={a1c1+a2c2:a1,a2∈Z, c1,c2∈C},\mathcal L_{\mathbb Z}^2(C)=\{a_1c_1+a_2c_2:a_1,a_2\in\mathbb Z,\ c_1,c_2\in C\},LZ2​(C)={a1​c1​+a2​c2​:a1​,a2​∈Z, c1​,c2​∈C}, LZ3(C)={x↦a1c(x)+a2c(x+δ):a1,a2∈Z, c∈C, δ>0}.\mathcal L_{\mathbb Z}^3(C)=\{x\mapsto a_1c(x)+a_2c(x+\delta):a_1,a_2\in\mathbb Z,\ c\in C,\ \delta>0\}.LZ3​(C)={x↦a1​c(x)+a2​c(x+δ):a1​,a2​∈Z, c∈C, δ>0}.

Lemma 4.1 equates monotonicity of every integer combination of two continuous monotonic nonconstant functions with affine dependence between them. Lemma 5.1 equates monotonicity of the translated-function hull with each function being affine or exponential; its rate may depend on the function. The source locations are pp.422–427, §§3–5.

Significance

The classification separates structural guarantees from favorable individual instances. A class that fails the displayed alternatives cannot guarantee a pure equilibrium for every admissible game. Conversely, either alternative guarantees termination of strict improvement paths as well as equilibrium existence. This gives a precise answer to the unrestricted consistency question posed by Harks and Klimm, without imposing nonnegative or increasing costs.

The mathematical results are published results, not new conjectures. The remaining task is their machine-checked proof. This draft supplies compiled definitions and theorem statements; the seven theorem bodies remain proof targets. Its reusable components include the finite weighted game model, universal class predicates, and three different integer hulls. Published pure-equilibrium and improvement-path definitions are reused through their existing interfaces.

Difficulty

Monotonicity of individual resource costs does not settle the unrestricted problem. The selected statements impose conditions on combinations of functions, and those conditions distinguish the allowed class-wide structure. In particular, separate exponential representations for every member do not establish the common-rate alternative. Another logical obstacle is that an improvement cycle alone need not rule out an equilibrium elsewhere in a game's profile space. The source's nonexistence arguments must exclude every feasible equilibrium, not just exhibit cycling behavior. These distinctions are visible in §§3–5.

The findings accompanying this mission record local issues in printed proofs separately from their theorem statements. Such issues do not authorize stronger hypotheses or weaker conclusions in the faithful targets.

Formalization scope

Players and facilities are indexed by finite initial segments with strictly positive sizes. Strategies are finite subsets, and feasible strategies are subtypes of the specified nonempty families. This represents every finite game up to relabeling. Demands are strictly positive nonnegative reals, loads are finite sums, and private costs are ordinary reals. Payoff-maximizing published definitions receive the negative of the private cost. Finite profile spaces justify the equivalence of the published infinite-path FIP convention and the paper's cycle convention.

Consistency is defined by quantification over all admissible games; neither potentials nor the classification are included in admissibility. The hulls are constructed from integer coefficients and the stated translates, without selecting only their monotonic members. Continuity is imposed on the whole nonnegative domain. These choices exclude vacuous proxy models and restricted strategy classes. The empty class and constant functions remain included. No asymptotic estimates or extracted constants occur.

The twelve new definition items precede the seven theorem items, and the six numbered source milestones retain their provenance. No optional variant is posed. The independent two-player characterization and the network and singleton results are outside the mission. In particular, the correction notice on p.436 concerning finite rather than polynomial termination does not introduce an algorithmic target here. Contributions should complete the faithful statements and their needed supporting theory while preserving these conventions.

Selected references

  • Tobias Harks and Max Klimm, On the Existence of Pure Nash Equilibria in Weighted Congestion Games, Mathematics of Operations Research 37(3), 419–436, 2012. Published article and correction notice. All theorem numbering and quotations use this published artifact.
22 thms3 active usersReviewed
Operations ResearchProbabilityStochastic Systems·Captain: Shuze Chen

Stochastic Networks XIV: Large Deviations for Queues with Many SourcesTextbook

Motivation

Communication connections can demand bandwidth at rates that fluctuate over time. Reserving every connection's peak rate can leave substantial capacity unused, while reserving only its mean rate allows temporary overloads and queueing delays. Effective bandwidth provides a way to express the statistical cost of a source in terms that can be used in admission decisions. Chapter 6 of Kelly and Yudovina's Stochastic Networks develops this question first for an instantaneous aggregate load and then for a resource with a buffer.

The buffered model distinguishes the number of connections from the number of connection classes. The number of classes stays fixed while capacity, buffer size, and the number of connections all grow together. The object of interest is the exponential rate of the probability that the workload exceeds the buffer level. This rate measures rare overloads on a scale where ordinary convergence of probabilities to zero loses the relevant information.

Setting

A source increment Xji[a,b]X_{ji}[a,b]Xji​[a,b] is the work arriving during an interval from connection iii of class jjj. The classes form a finite set JJJ. A source supplies nonnegative, additive increments, with no work on an interval of length zero. Each interval workload is a measurable real random variable. Different source processes are independent, copies within one class have the same process law, and increments have stationary distributions: the law of an interval's workload depends only on its duration. Independence between increments of one source is not required.

Let njn_jnj​ be the natural number of class-jjj sources in a base system. At positive integer scale NNN, there are njNn_jNnj​N copies. The aggregate arrival is

SN[a,b]=∑j∈J∑i=1njNXji[a,b].S^N[a,b]=\sum_{j\in J}\sum_{i=1}^{n_jN}X_{ji}[a,b].SN[a,b]=j∈J∑​i=1∑nj​N​Xji​[a,b].

A server of capacity CNCNCN, where C>0C>0C>0, processes this work. Its infinite-past workload at time zero is the random variable

QN(0)=sup⁡t≥0{SN[−t,0]−CNt}.Q^N(0)=\sup_{t\ge0}\{S^N[-t,0]-CNt\}.QN(0)=t≥0sup​{SN[−t,0]−CNt}.

This is the construction in equation (6.4), not an independently chosen stationary queue size. It can be infinite. With a positive base buffer BBB, the overflow probability is LN=P(QN(0)>BN)L_N=P(Q^N(0)>BN)LN​=P(QN(0)>BN).

The logarithmic moment generating function of a class-jjj increment is

Mj(s,t)=log⁡Eexp⁡(sXj1[0,t]).M_j(s,t)=\log\mathbb E\exp(sX_{j1}[0,t]).Mj​(s,t)=logEexp(sXj1​[0,t]).

Exponential moments are assumed finite locally around zero for each finite duration, following the chapter's MGF convention; a larger tilt may have infinite expectation. The quantity Mj(s,t)M_j(s,t)Mj​(s,t) is the nonsingular expression for the product stαj(s,t)st\alpha_j(s,t)stαj​(s,t) in the book's effective-bandwidth formula.

Formalization targets

The goal is Theorem 6.10, printed page 145 of the supplied Lecture Notes PDF:

lim⁡N→∞1Nlog⁡LN=sup⁡t≥0inf⁡s≥0[∑j∈JnjMj(s,t)−s(B+Ct)].\lim_{N\to\infty}\frac1N\log L_N =\sup_{t\ge0}\inf_{s\ge0} \left[\sum_{j\in J}n_jM_j(s,t)-s(B+Ct)\right].N→∞lim​N1​logLN​=t≥0sup​s≥0inf​​j∈J∑​nj​Mj​(s,t)−s(B+Ct)​.

The supremum over duration remains outside the infimum over tilt. Both the continuous time domain and the infinite horizon are part of the target.

Three source milestones accompany the goal. Equation (6.1) asserts, for a measurable real random variable YYY and s≥0s\ge0s≥0,

P(Y>0)=E1{Y>0}≤EesY,P(Y>0)=\mathbb E\mathbf1_{\{Y>0\}}\le\mathbb E e^{sY},P(Y>0)=E1{Y>0}​≤EesY,

including infinite exponential expectations. Theorem 6.2 asserts the exact logarithmic rate for an iid sum exceeding ncncnc. Its assumptions include a mean below ccc, a positive probability of exceeding ccc, local MGF finiteness, and an optimizing tilt in the interior of the finite-MGF domain. Exercise 6.9 gives both the two-sequence and finite-sum largest-term principles, with finite real rates and positive sequences. It makes no assertion about a countable sum.

Significance

The goal relates the statistical characteristics of individual connections to the overload behavior of a large system. It retains duration as a variable, allowing temporal dependence within a connection to affect the rate. A fixed-time tail probability alone does not describe the workload accumulated from an unlimited past. This distinction is central to the buffered model in Chapter 6.

The formal deliverable specifies the source family, its scaling, the workload construction, and the variational expression in one consistent setting. It also separates extended expectations from finite real expectations, so the meaning of a rare event does not change when its probability is zero. These definitions can support later work on queueing large deviations without requiring a finite-state Markov model.

The local theorem files are declarations to be proved, not completed proofs. A published proved Chernoff bound is retained as a reference for the integrable exponential case. The separately published open Cramér theorem assumes finiteness at every real tilt and a closed tail event; it is not substituted for the chapter's local-MGF, strict-tail statement.

Difficulty

The source explicitly gives only a sketch for Theorem 6.10. Fixed-time exponential limits do not by themselves determine the exponential rate of a sum over infinitely many times. Exercise 6.9 establishes a finite-sum result, so it cannot close this gap. The continuous-time workload also raises a measurability and time-discretization issue. Finding F1 records the missing justification with an explicit array of exponentially small terms whose count grows exponentially.

Finding F4 gives an explicit counterexample to the printed goal, even with positive buffer and mean load below capacity. Independent sources have uniformly random phases of a periodic arrival rate taking values 0, 1, and 2. Each source contributes at most one unit of net input over any interval, so with B=C=1B=C=1B=C=1 the strict overflow probability is zero at every scale. At duration 2, however, the maximum input 3 has probability 1/51/51/5, giving a finite variational value −log⁡5-\log 5−log5. The faithful goal is retained as printed and is expected to be disproved; no corrected variant is proposed. This is a failure of the fixed-time application of Cramér’s theorem at a support endpoint, separate from F1’s infinite-time gap.

Finding F2 concerns a different finite-sample step in the proof of Cramér's theorem: convergence of a tilted-window probability to one half does not ensure it is at least one half for a given sample size. The limiting theorem is retained. Neither finding is converted into an extra hypothesis or a variant. The goal carries no uniform temporal decay estimate, mixing assumption, or fixed-time large-deviation conclusion as an assumption.

Formalization scope

The formalization uses Mathlib probability measures, independence and equality-in-distribution predicates, nonnegative Lebesgue integrals, and extended-real order topology. Whole source paths are independent; this is stronger information than independence of one chosen interval's workloads. Natural multiplicities provide exactly njNn_jNnj​N copies without rounding. Source indices begin at zero, and the asymptotic scale is represented as N+1N+1N+1 to avoid a zero denominator.

The queue supremum is over all nonnegative real times and takes values in EReal. Zero overflow probability has logarithm −∞-\infty−∞; infinite exponential expectation has logarithm +∞+\infty+∞. The rate subtracts only finite linear terms. Zero multiplicities contribute zero, including when an unused source has an infinite MGF. At zero time or zero tilt, the log MGF is zero under the source assumptions. No division by ststst is introduced.

Nonnegative additive increments use the usual half-open interval convention for endpoint arrivals. Measurability of the constructed workload is explicit, as required for the source's random-variable language. The model API also requires a probability measure and the relevant measurability when forming an overflow probability or exponential rate. Capacity and buffer are positive; F3 records a deterministic counterexample to extending the goal to zero buffer. Empty class sets and zero source counts remain permitted and give no overflow. For Exercise 6.9, positivity and a nonempty finite index set prevent default logarithms or maxima.

The goal must not be replaced by a finite-horizon queue, a deterministic drift inequality, or a hypothesis already asserting the desired asymptotic. No selected result uses an unspecified asymptotic constant, so there is no O(⋅)O(\cdot)O(⋅) constant to instantiate. No variant is posed. The model module supplies real definition bodies; theorem statements expand the relevant formulas so standalone blind read-backs can inspect their meaning without resolving unpublished imports.

Selected references

  • F. P. Kelly and E. Yudovina, Stochastic Networks, Cambridge University Press, 2014. DOI. The pinned supplied artifact is titled Lecture Notes on Stochastic Networks: Chapter 6, printed pages 133–148, PDF pages 141–156. Correspondence with a particular published printing is not asserted. PDF SHA-256: ec271d555059aee58613e5e9a98b8346214b16185c527314f5d94c1ac8b17b6a.
6 thms3 active usersReviewed
Markov ChainOperations ResearchProbability+1·Captain: Shuze Chen

Stochastic Networks X: Stationary Open Migration Processes Under Time ReversalTextbook

Motivation

A network of queues records both how many customers occupy each location and how they move between locations. These are different kinds of information. A simple distribution for the occupancies at one time need not make the arrival streams simple, or make the queues independent over time. Open migration processes provide a setting in which the distinction can be studied precisely: customers can move through a finite network, enter from outside, and eventually leave. Chapter 2 of Kelly and Yudovina, Stochastic Networks develops their equilibrium structure.

The target concerns what an observer sees when a stationary network is run backwards. It says that the reversed random process belongs to the same class of models, even when its rates differ from those of the original process. This structural result is the setting for the source's subsequent conclusion about Poisson exit streams. The mission treats the process statement itself, keeping the distinction between an equilibrium rate calculation and a statement about a random trajectory.

Setting

There are a finite positive number JJJ of colonies. The state is n=(n1,…,nJ)∈NJn=(n_1,\ldots,n_J)\in\mathbb N^Jn=(n1​,…,nJ​)∈NJ, where njn_jnj​ counts individuals at colony jjj. There is no upper bound on an occupancy or on the total population. A transition can transfer an individual from colony jjj to a different colony kkk, remove one from the system at colony jjj, or introduce one at colony kkk.

The corresponding rates are λjkφj(nj)\lambda_{jk}\varphi_j(n_j)λjk​φj​(nj​), μjφj(nj)\mu_j\varphi_j(n_j)μj​φj​(nj​), and νk\nu_kνk​. The coefficients are nonnegative, λjj=0\lambda_{jj}=0λjj​=0, and the service factors satisfy φj(0)=0\varphi_j(0)=0φj​(0)=0 and φj(r)>0\varphi_j(r)>0φj​(r)>0 when r≥1r\ge1r≥1. A departure requires an individual to be present. Immigration rates do not depend on the occupancy. These are the rates in Section 2.4 of the supplied source, printed pages 30–31.

A Markov process here consists of measurable random variables on one probability space, indexed by real time. Its conditional future distributions depend on the most recent state, through a time-homogeneous transition function. Transition rates are its right-hand infinitesimal transition probabilities. The standing assumptions from Section 1.1 are explicit: the process is irreducible, every state has a strictly positive finite exit rate, and sample paths have only finitely many jumps on each bounded interval. A stationary law is a positive normalized mass function π\piπ giving the distribution at every time.

Formalization targets

The goal is Theorem 2.9, printed page 32 of the supplied PDF:

(n(t))t∈R stationary open migration⟹(n(−t))t∈R stationary open migration.(n(t))_{t\in\mathbb R}\text{ stationary open migration} \quad\Longrightarrow\quad (n(-t))_{t\in\mathbb R}\text{ stationary open migration}.(n(t))t∈R​ stationary open migration⟹(n(−t))t∈R​ stationary open migration.

Three milestones support this target. The partial-balance equations (2.3) and (2.4) are grouped as one milestone because one published theorem supplies both identities. They express equilibrium flux balance for transitions associated with a colony and with the outside world. Theorem 2.8 gives the normalized product-form distribution. With positive traffic parameters αj\alpha_jαj​ satisfying

αj(μj+∑kλjk)=νj+∑kαkλkj,\alpha_j\left(\mu_j+\sum_k\lambda_{jk}\right) =\nu_j+\sum_k\alpha_k\lambda_{kj},αj​(μj​+k∑​λjk​)=νj​+k∑​αk​λkj​,

and finite normalizing sums gjg_jgj​, that distribution is

gj=∑m=0∞αjm∏r=1mφj(r),π(n)=∏jgj−1αjnj∏r=1njφj(r).g_j=\sum_{m=0}^{\infty}\frac{\alpha_j^m}{\prod_{r=1}^m\varphi_j(r)}, \qquad \pi(n)=\prod_j g_j^{-1}\frac{\alpha_j^{n_j}}{\prod_{r=1}^{n_j}\varphi_j(r)}.gj​=m=0∑∞​∏r=1m​φj​(r)αjm​​,π(n)=j∏​gj−1​∏r=1nj​​φj​(r)αjnj​​​.

The third milestone, Proposition 1.1, concerns a stationary process on a countable state space. Its reversed process has the same stationary law and rates

q′(i,j)=π(j)q(j,i)π(i).q'(i,j)=\frac{\pi(j)q(j,i)}{\pi(i)}.q′(i,j)=π(i)π(j)q(j,i)​.

All three source statements are in Kelly and Yudovina, printed pages 16–17 and 31. The goal does not assume the product form, a reverse-process Markov property, or any of the reverse-rate identities.

Significance

The result identifies a class of stochastic networks that remains closed under reversal of stationary time. It does not assert detailed balance or equality of the original and reversed rates. It also does not infer independence of colony trajectories from independence of occupancies at one time; the source expressly distinguishes these statements on printed page 32. This separation is needed when interpreting the Poisson exit-stream consequence on printed page 33 of the source.

Published formal results already supply partial balance, normalized full balance, and the algebraic reversed migration rates. They are included as references rather than repeated as new theorem statements. The remaining formal targets concern the actual countable-state random processes: the Markov property of the reversal and preservation of the open-migration class. The new definition layer also provides finite-cylinder and nonexplosive-path specifications that can be reused for other countable-state stationary models.

Difficulty

A formula for a reversed rate matrix alone does not establish a theorem about the reversed process. The latter has finite-dimensional distributions, measurable coordinates, and nonexplosive paths. These must all be connected to the rates. The occupancy space is countably infinite even though the number of colonies is finite, so finite-state reversal theorems do not directly cover the goal. Similarly, assuming the candidate product distribution as part of the meaning of a stationary migration process would omit part of the source's claim. The definition deliberately leaves the stationary law unspecified.

Formalization scope

Colonies are represented by Fin J\mathrm{Fin}\,JFinJ with J>0J>0J>0; states are unrestricted functions from this type to natural numbers. The zero-based colony labels differ only typographically from the source's labels 1,…,J1,\ldots,J1,…,J. The exact published migration operators and rate functions are reused. Their natural-number subtraction is protected by vanishing service factors at zero and a zero routing diagonal. Empty products equal one. Normalizing sums in the referenced product-form result use HasSum, so divergent real sums cannot acquire a default value and masquerade as finite normalizers.

The process definitions use probability measures, measurable coordinates, stochastic transition functions, finite-cylinder identities, and locally finite jump paths. Cylinder identities avoid conditioning by division at null events. The state space is countable with measurable singletons, and rate rows are explicitly summable. Positivity of the stationary mass function prevents a zero denominator in the reversal formula. Paths may take either adjacent value at a jump, accommodating the reversal of the right-continuous endpoint convention; isolated zero-duration spikes are excluded.

The goal must establish migration dynamics for the actual map t↦n(−t)t\mapsto n(-t)t↦n(−t); an algebraic rate identity or independence at a single time is not a substitute. No asymptotic constants or failure probabilities occur in these targets. The infinite-colony extension, Poisson departure processes, Little's law, Bartlett's theorem, and renewal-reward variants are outside this mission. The findings register preserves observations about out-of-scope source displays, but no variant theorem is proposed. Contributions to the countable-state stochastic foundations and proofs of the two draft theorem statements are within scope.

Selected references

  • F. P. Kelly and E. Yudovina, Stochastic Networks, Cambridge University Press, 2014. DOI. The pinned supplied artifact is titled Lecture Notes on Stochastic Networks: Section 1.1 and Proposition 1.1, printed pages 13–17 (PDF 21–25); Section 2.4, equations (2.2)–(2.4), Theorems 2.8–2.9, printed pages 30–33 (PDF 38–41). Equivalence to a particular published printing is unverified. PDF SHA-256: ec271d555059aee58613e5e9a98b8346214b16185c527314f5d94c1ac8b17b6a.
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Robust Optimization IX: Safe Matrix Chance ConstraintsTextbook

Matrix inequalities under random perturbations

A semidefinite constraint asks whether a symmetric matrix is positive semidefinite: every vector must have a nonnegative quadratic form under that matrix. In optimization, its entries can depend on a decision and on uncertain inputs. Requiring the constraint for every possible input can be restrictive, especially when rare inputs have very large magnitude. A chance constraint instead requires the matrix inequality to hold with a specified probability. Chapter 10 of Ben-Tal, El Ghaoui and Nemirovski, Robust Optimization develops safe approximations for such constraints, including conic quadratic constraints represented through symmetric matrices.

The question here is how a known probability of a moderate matrix perturbation can imply a much higher probability at a larger threshold. The chapter gives explicit answers for bounded independent perturbations and for independent standard normal perturbations. The goal is its Corollary 10.1.3, including both distributional cases and the possibility that the reference matrix is singular.

Symmetric matrices, probability, and the variance certificate

Let A,B1,…,BLA,B_1,\ldots,B_LA,B1​,…,BL​ be deterministic symmetric real m×mm\times mm×m matrices, with m,L≥1m,L\ge1m,L≥1. The random perturbation is

S=∑ℓ=1LζℓBℓ.S=\sum_{\ell=1}^L\zeta_\ell B_\ell.S=ℓ=1∑L​ζℓ​Bℓ​.

The Loewner order C⪯DC\preceq DC⪯D means that D−CD-CD−C is positive semidefinite. Thus the event −tA⪯S⪯tA-tA\preceq S\preceq tA−tA⪯S⪯tA controls the perturbation simultaneously in every vector direction. For normalized matrices, ∥S∥\|S\|∥S∥ denotes the operator norm for Euclidean vectors, rather than a maximum entry or a row-sum norm.

The random coordinates are measurable and independent on a probability space. Under assumption A.I they have zero means and satisfy ∣ζℓ∣≤1|\zeta_\ell|\le1∣ζℓ​∣≤1 almost surely. Under A.II each has the standard normal law N(0,1)N(0,1)N(0,1). The deterministic variance certificate is

∃Y1,…,YL:(YℓBℓBℓA)⪰0(1≤ℓ≤L),∑ℓYℓ⪯A.\exists Y_1,\ldots,Y_L:\quad \begin{pmatrix}Y_\ell&B_\ell\\B_\ell&A\end{pmatrix}\succeq0 \quad(1\le\ell\le L),\qquad \sum_\ell Y_\ell\preceq A.∃Y1​,…,YL​:(Yℓ​Bℓ​​Bℓ​A​)⪰0(1≤ℓ≤L),ℓ∑​Yℓ​⪯A.

This is precisely system (10.1.13) in the source. A separate premise supplies the base probability

Pr⁡{−ΥA⪯S⪯ΥA}≥χ,\Pr\{-\Upsilon A\preceq S\preceq\Upsilon A\}\ge\chi,Pr{−ΥA⪯S⪯ΥA}≥χ,

where Υ>0\Upsilon>0Υ>0 and χ>0\chi>0χ>0. Neither this probability premise nor the certificate contains the amplified probability conclusion.

Write T(t)=Pr⁡{G>t}T(t)=\Pr\{G>t\}T(t)=Pr{G>t} for G∼N(0,1)G\sim N(0,1)G∼N(0,1), and qqq for its inverse upper-tail quantile. The book writes these functions as Erf and ErfInv. Its Erf is a one-sided upper Gaussian tail; substituting the common analytic error function would change every Gaussian bound.

Formalization targets

The goal, Corollary 10.1.3, asserts that under A.I, for every Ω>Υ\Omega>\UpsilonΩ>Υ,

Pr⁡{−ΩA⪯S⪯ΩA}≥1−1χexp⁡(−(Ω−Υ)216).\Pr\{-\Omega A\preceq S\preceq\Omega A\} \ge1-\frac1\chi\exp\left(-\frac{(\Omega-\Upsilon)^2}{16}\right).Pr{−ΩA⪯S⪯ΩA}≥1−χ1​exp(−16(Ω−Υ)2​).

Under A.II and the additional condition χ>1/2\chi>1/2χ>1/2, it asserts

Pr⁡{−ΩA⪯S⪯ΩA}≥1−T(q(1−χ)+(Ω−Υ)max⁡{1,q(1−χ)/Υ}).\Pr\{-\Omega A\preceq S\preceq\Omega A\} \ge1-T\left(q(1-\chi)+(\Omega-\Upsilon) \max\{1,q(1-\chi)/\Upsilon\}\right).Pr{−ΩA⪯S⪯ΩA}≥1−T(q(1−χ)+(Ω−Υ)max{1,q(1−χ)/Υ}).

Both conclusions retain the constants and strict threshold of equations (10.1.15)–(10.1.16).

Three source-numbered milestones support this goal. Theorem 10.1.1 concerns symmetric BℓB_\ellBℓ​ with ∑Bℓ2⪯I\sum B_\ell^2\preceq I∑Bℓ2​⪯I and defines χ=Pr⁡{∥S∥≤Υ}>0\chi=\Pr\{\|S\|\le\Upsilon\}>0χ=Pr{∥S∥≤Υ}>0. Its bounded-case conclusion is

Pr⁡{∥S∥>Ω}≤χ−1e−(Ω−Υ)2/16,Ω>Υ.\Pr\{\|S\|>\Omega\}\le\chi^{-1}e^{-(\Omega-\Upsilon)^2/16},\qquad \Omega>\Upsilon.Pr{∥S∥>Ω}≤χ−1e−(Ω−Υ)2/16,Ω>Υ.

Theorem B.5.1 concerns a closed convex set Q⊆RmQ\subseteq\mathbb R^mQ⊆Rm with standard Gaussian mass at least χ>1/2\chi>1/2χ>1/2. It asserts that QQQ contains the centered ball of radius q(1−χ)>0q(1-\chi)>0q(1−χ)>0. If it contains a centered ball of radius r≥q(1−χ)r\ge q(1-\chi)r≥q(1−χ), then for α≥1\alpha\ge1α≥1,

Pr⁡{G∉αQ}≤T(q(1−χ)+(α−1)r)≤T(αq(1−χ))≤12e−α2q(1−χ)2/2.\Pr\{G\notin\alpha Q\}\le T(q(1-\chi)+(\alpha-1)r) \le T(\alpha q(1-\chi))\le\tfrac12e^{-\alpha^2q(1-\chi)^2/2}.Pr{G∈/αQ}≤T(q(1−χ)+(α−1)r)≤T(αq(1−χ))≤21​e−α2q(1−χ)2/2.

Its further conclusion covers centered Gaussians with arbitrary positive semidefinite covariance: an outside probability at most δ<1/2\delta<1/2δ<1/2 becomes at most T(αq(δ))≤12e−α2q(δ)2/2T(\alpha q(\delta))\le\tfrac12e^{-\alpha^2q(\delta)^2/2}T(αq(δ))≤21​e−α2q(δ)2/2 after dilation. This clause includes degenerate covariance matrices.

Theorem 10.1.2 is the normalized Gaussian matrix milestone. With the same variance normalization and exact base mass χ>1/2\chi>1/2χ>1/2, it states, now for Ω≥Υ\Omega\ge\UpsilonΩ≥Υ,

Pr⁡{∥S∥>Ω}≤T(q(1−χ)+(Ω−Υ)max⁡{1,Υ−1q(1−χ)})≤e−Ω2Υ−2q(1−χ)2/2.\Pr\{\|S\|>\Omega\}\le T\left(q(1-\chi)+(\Omega-\Upsilon)\max\{1,\Upsilon^{-1}q(1-\chi)\}\right) \le e^{-\Omega^2\Upsilon^{-2}q(1-\chi)^2/2}.Pr{∥S∥>Ω}≤T(q(1−χ)+(Ω−Υ)max{1,Υ−1q(1−χ)})≤e−Ω2Υ−2q(1−χ)2/2.

What a formal development supplies

The chapter’s bounds connect a matrix certificate and a base confidence level to explicit larger-threshold confidence guarantees. They preserve information about the reference matrix, including its null directions. A statement requiring positive definiteness would exclude part of this conclusion.

These are established textbook results whose Lean proofs remain the targets of this mission. The draft supplies concrete definitions and open theorem statements, not completed proofs. Mathlib already provides probability measures, normal distributions, matrix positivity, and a semidefinite Schur-complement equivalence. The published theorem PinningSync.Tree.lemma_2_13 supplies the positive-definite Schur-complement branch as a reference; it is not presented as a substitute for the full semidefinite lemma.

Difficulty

The target combines probabilistic concentration with inequalities that must hold in every matrix direction. Entrywise bounds do not state the same event. Likewise, an invertible reference matrix is a restricted case of the goal. The Gaussian branch also requires exact control of inverse-tail conventions and dilation probabilities for general closed convex sets. The source’s proof of Theorem B.5.1(i) has inconsistent tail arguments in its separating-halfspace paragraph, recorded as a proof warning; the theorem statement retains the printed q(1−χ)q(1-\chi)q(1−χ).

Formalization scope

All matrices are real, finite, and explicitly symmetric in the theorems. Matrix and perturbation dimensions are positive; indexing by Fin changes only the origin of the indices. The setup uses Mathlib’s positive-semidefinite predicate directly. The two matrix inequalities are defined by their positive-semidefinite differences, and the variance certificate is an existential block-matrix condition. The Gaussian geometric theorem uses the concrete standard and multivariate Gaussian measures on Euclidean space, with a positive-semidefinite covariance premise.

Formalization Note. Equation (2.3.22) specifies the inverse tail on (0,1)(0,1)(0,1), while the later statements allow base mass one and failure probability zero. The draft retains those cases by using the extended-real inverse quantile, with q(0)=+∞q(0)=+\inftyq(0)=+∞, T(+∞)=0T(+\infty)=0T(+∞)=0, and the limiting exponential envelope zero at infinity. An infinite-radius centered ball is the whole space. All displayed formulas agree with the source on finite quantile arguments. This endpoint interpretation is recorded in the findings for review, rather than imposing an unprinted χ<1\chi<1χ<1 restriction.

The reusable components are the matrix perturbation, the two-sided order event, the block certificate, and the Gaussian tail conventions. Proof contributions must establish the full statements with their constants and endpoints. No variants are posed in this mission.

Selected references

  • A. Ben-Tal, L. El Ghaoui and A. Nemirovski, Robust Optimization, Princeton University Press, 2009. DOI. Chapter 10, printed pp. 237–241; Appendix B.5, printed p. 508; equation (2.3.22), printed p. 39.
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Convex OptimizationOperations ResearchOptimization·Captain: Shuze Chen

Robust Optimization I: Conic Representations of Robust Linear ConstraintsTextbook

Reliable linear constraints under uncertain data

A production or allocation decision can satisfy a linear constraint for nominal data and violate it when those data change. Robust optimization asks for a decision that satisfies the constraint for every realization in a prescribed uncertainty set. The uncertainty set is part of the model: the requirement does not attach probabilities to its elements, and it does not permit a small violation at an unfavorable realization. Chapter 1 of Ben-Tal, El Ghaoui and Nemirovski, Robust Optimization develops this interpretation for linear optimization.

This requirement initially gives infinitely many inequalities, even when the decision vector has only a few coordinates. The chapter's representation results identify uncertainty descriptions for which those inequalities can be replaced exactly by finite systems. The replacement matters to applications because it preserves the set of admissible decisions while expressing it in the language of linear, conic quadratic, or semidefinite optimization.

Affine uncertainty and lifted descriptions

Let x∈Rnx\in\mathbb R^nx∈Rn be the decision vector and z∈RLz\in\mathbb R^Lz∈RL the perturbation. The nominal coefficients are a0∈Rna^0\in\mathbb R^na0∈Rn and b0∈Rb^0\in\mathbb Rb0∈R, with shifts aℓ,bℓa^\ell,b^\ellaℓ,bℓ for each perturbation coordinate. The robust linear constraint is

(a0)Tx+∑ℓ=1Lzℓ(aℓ)Tx≤b0+∑ℓ=1Lzℓbℓfor every z∈Z.(a^0)^Tx+\sum_{\ell=1}^Lz_\ell(a^\ell)^Tx \le b^0+\sum_{\ell=1}^Lz_\ell b^\ell \qquad\text{for every }z\in Z.(a0)Tx+ℓ=1∑L​zℓ​(aℓ)Tx≤b0+ℓ=1∑L​zℓ​bℓfor every z∈Z.

A lifted conic description specifies the perturbation set by

Z={z∈RL:∃v∈Ru, Pz+Qv+p∈K}.Z=\{z\in\mathbb R^L:\exists v\in\mathbb R^u,\ Pz+Qv+p\in K\}.Z={z∈RL:∃v∈Ru, Pz+Qv+p∈K}.

Here P,QP,QP,Q are linear coefficient arrays, ppp is an offset, and KKK is a cone. The variable vvv describes the uncertainty set; it is not a decision made after uncertainty is observed. The general theorem assumes that KKK is closed, convex and pointed, with nonempty interior. The perturbation set is nonempty. For a nonpolyhedral cone, the description must have a point strictly inside the cone.

An equivalent representation has additional variables but projects to precisely the original feasible set. The interpretation is existential: a feasible decision xxx must admit a certificate, and every feasible pair must project to a robust feasible xxx. This is Definition 1.3.1 of the source, not a sufficient-condition approximation.

Formalization targets

The goal is Corollary 1.3.5, printed page 21. If the description uses a nonnegative orthant, a product of Lorentz cones, or a positive semidefinite cone, the robust constraint has an explicit LP, SOCP, or SDP representation, respectively. Strict feasibility is required for the latter two cases. With auxiliary variable yyy, the system is

pTy+(a0)Tx≤b0,QTy=0,p^Ty+(a^0)^Tx\le b^0,\qquad Q^Ty=0,pTy+(a0)Tx≤b0,QTy=0, (PTy)ℓ+(aℓ)Tx=bℓ(1≤ℓ≤L),y∈K.(P^Ty)_\ell+(a^\ell)^Tx=b^\ell\quad(1\le\ell\le L),\qquad y\in K.(PTy)ℓ​+(aℓ)Tx=bℓ(1≤ℓ≤L),y∈K.

The goal includes the polynomial size of this representation and the explicit dependence of its coefficients on the input data. It also records preservation of the set of feasible objective values for an objective depending only on xxx.

Theorem 1.3.4 is the general supporting target. It gives the same system with y∈K∗y\in K^*y∈K∗, where K∗={y:yTz≥0 for every z∈K}K^*=\{y:y^Tz\ge0\text{ for every }z\in K\}K∗={y:yTz≥0 for every z∈K}, and allows either a polyhedral cone or a strictly feasible description. The two introductory examples give concrete representation targets:

(a0)Tx+∑ℓ∣(aℓ)Tx−bℓ∣≤b0for Z=[−1,1]L,(a^0)^Tx+\sum_\ell|(a^\ell)^Tx-b^\ell|\le b^0 \quad\text{for }Z=[-1,1]^L,(a0)Tx+ℓ∑​∣(aℓ)Tx−bℓ∣≤b0for Z=[−1,1]L, (a0)Tx+Ω∑ℓ((aℓ)Tx−bℓ)2≤b0for Z={z:∥z∥2≤Ω}.(a^0)^Tx+\Omega\sqrt{\sum_\ell((a^\ell)^Tx-b^\ell)^2}\le b^0 \quad\text{for }Z=\{z:\|z\|_2\le\Omega\}.(a0)Tx+Ωℓ∑​((aℓ)Tx−bℓ)2​≤b0for Z={z:∥z∥2​≤Ω}.

The box target includes its further representation by finitely many linear inequalities with auxiliary upper bounds on the absolute values. These are Examples 1.3.2 and 1.3.3, not additional general duality assumptions.

What the representation provides

The result identifies the finite certificate system appropriate to each uncertainty model. It distinguishes an exact reformulation from a conservative replacement that could exclude valid decisions. Because the original decision variables remain present, an objective can be retained without interpreting the auxiliary certificate as an additional physical decision.

The mathematical results are established textbook results. The work requested here is their formal proof against explicit Lean statements. The resulting definitions expose affine uncertainty, lifted perturbation sets and finite certificate systems for reuse. Published good-cone and dual-cone definitions are already available and are imported; the theorem statements in this mission remain open proof targets.

Difficulty and boundary behavior

The equivalence requires existence of a finite certificate, not merely a sequence approaching a limiting objective value. Nonpolyhedral descriptions can fail to admit the asserted certificate without strict feasibility. In contrast, the polyhedral case does not need a strictly feasible point, so imposing that condition uniformly would lose part of the source result.

There is also a distinction between a finite worst-case value and a perturbation attaining it. The proof on printed page 20 writes a maximization problem and then discusses its optimal value; this does not require primal attainment. The formal target uses universal feasibility directly. The local findings record an explicit nonattainment example, without establishing a gap in the duality argument.

Formalization scope

All coordinates are real and finite. Nominal coefficients are stored separately from perturbation shifts. Lorentz blocks contain a distinguished scalar coordinate and a finite vector part; their Euclidean norm is the square root of a sum of squares. PSD coefficients are symmetric matrices, and pairings sum all matrix entries, giving the trace pairing for symmetric inputs. Strict feasibility in that case means positive definiteness in the symmetric ambient space.

The representation is built from the coefficient arrays themselves. Robust feasibility is defined independently by universal quantification over perturbations; it is never defined as certificate existence. No rank condition is imposed on PPP or QQQ. Nonnegative ball radii include zero, and zero-dimensional coordinate lists retain their ordinary empty-sum interpretation.

Formalization Note The explicit system has one scalar inequality, u+Lu+Lu+L scalar equalities, and one standard cone block. If NNN is its number of auxiliary scalar coordinates and qqq its structural cone description length, the chosen dense counts are

I=1+n+L+u+N+(L+1)(n+1)+(L+u+1)N+q,I=1+n+L+u+N+(L+1)(n+1)+(L+u+1)N+q,I=1+n+L+u+N+(L+1)(n+1)+(L+u+1)N+q, O=n+N+(u+L+1)(n+N+1)+q.O=n+N+(u+L+1)(n+N+1)+q.O=n+N+(u+L+1)(n+N+1)+q.

The size target is O≤4I2O\le4I^2O≤4I2, an explicit witness to the book's polynomial-size assertion. The constant is encoding bookkeeping, not a numerical complexity constant quoted from the book. PSD storage uses k2k^2k2 coordinates, including symmetric duplicates. These counts concern the finite representation, not bit complexity or the time needed to solve it.

Selected references

  • Aharon Ben-Tal, Laurent El Ghaoui and Arkadi Nemirovski, Robust Optimization, Princeton University Press, 2009, Chapter 1, Definition 1.3.1, Examples 1.3.2–1.3.3, Theorem 1.3.4 and Corollary 1.3.5, printed pages 17–21. DOI.
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AlgebraQuantum InformationRepresentation Theory·Captain: mikedeng1

Structure and Properties of the Algebra of Partially Transposed Permutation Operators: A = M ⊕ S, M = ⊕ U(α) with U(α) ≅ M(rank Q(α), ℂ), and S ≅ ⊕_{h(ν)<d} M(dim ψ^ν, ℂ)Research Paper

Motivation

Permutation operators encode the symmetries of many identical quantum systems. When one tensor factor is transposed, the resulting operators occur in questions about the commutant of mixed tensor representations and about partially transposed quantum states. The usual symmetric-group algebra no longer describes their multiplication: a product can acquire a factor equal to the local dimension ddd. Mozrzymas, Horodecki, and Studziński determined the full algebraic structure of their span in their 2014 paper. Their description identifies its simple components even when a small local dimension makes the natural spanning family linearly dependent.

Setting

Let d≥1d\ge1d≥1 and n=m+2≥2n=m+2\ge2n=m+2≥2. On nnn tensor factors of Cd\mathbb C^dCd, the permutation operator V(σ)V(\sigma)V(σ) moves the computational-basis tensor indexed by (i1,…,in)(i_1,\ldots,i_n)(i1​,…,in​) to the tensor indexed by (iσ−1(1),…,iσ−1(n))(i_{\sigma^{-1}(1)},\ldots,i_{\sigma^{-1}(n)})(iσ−1(1)​,…,iσ−1(n)​). Write tnt_ntn​ for matrix transposition on the last tensor factor only. The object of this mission is the complex operator algebra

A=Antn(d)=span⁡C{V(σ)tn:σ∈S(n)}.A=A_n^{t_n}(d)=\operatorname{span}_{\mathbb C}\{V(\sigma)^{t_n}:\sigma\in S(n)\}.A=Antn​​(d)=spanC​{V(σ)tn​:σ∈S(n)}.

The subspace MMM is spanned by those V(σ)tnV(\sigma)^{t_n}V(σ)tn​ for which σ(n)≠n\sigma(n)\ne nσ(n)=n. Its complement SSS in the result is an ideal that annihilates MMM on both sides. The permutations of the first n−2n-2n−2 positions act on (Cd)⊗(n−2)(\mathbb C^d)^{\otimes(n-2)}(Cd)⊗(n−2). For each irreducible representation φα\varphi^\alphaφα of S(n−2)S(n-2)S(n−2) that occurs in this action, write wα=dim⁡φαw^\alpha=\dim\varphi^\alphawα=dimφα. Definition 40 constructs operators uijab(α)u^{ab}_{ij}(\alpha)uijab​(α) from their matrix coefficients, the permutation operators, and partial transposition. Their span is U(α)U(\alpha)U(α).

Definition 29 assigns to α\alphaα a block matrix Q(α)Q(\alpha)Q(α) indexed by (a,i)(a,i)(a,i) and (b,j)(b,j)(b,j), where 1≤a,b≤n−11\le a,b\le n-11≤a,b≤n−1 and 1≤i,j≤wα1\le i,j\le w^\alpha1≤i,j≤wα. Its (a,b)(a,b)(a,b) block is dδabφα((a n−1)(ab)(b n−1))d^{\delta_{ab}}\varphi^\alpha((a\ n-1)(ab)(b\ n-1))dδab​φα((a n−1)(ab)(b n−1)), so every diagonal block is ddd times the identity. Finally, a partition ν\nuν of n−1n-1n−1 labels an irreducible representation ψν\psi^\nuψν of S(n−1)S(n-1)S(n−1); h(ν)h(\nu)h(ν) counts the rows of its Young diagram.

Formalization targets

Structure theorem

Theorem 30 asserts that AAA splits into mutually annihilating ideals, and that those ideals split further into full matrix algebras:

A=M⊕S,M=⨁φα⊆Vd[S(n−2)]U(α),U(α)≅Mrank⁡Q(α)(C),S≅⨁ν⊢n−1h(ν)<dMdim⁡ψν(C).A=M\oplus S,\qquad M=\bigoplus_{\varphi^\alpha\subseteq V_d[S(n-2)]}U(\alpha),\qquad U(\alpha)\cong M_{\operatorname{rank}Q(\alpha)}(\mathbb C),\qquad S\cong\bigoplus_{\substack{\nu\vdash n-1\\h(\nu)<d}}M_{\dim\psi^\nu}(\mathbb C).A=M⊕S,M=φα⊆Vd​[S(n−2)]⨁​U(α),U(α)≅MrankQ(α)​(C),S≅ν⊢n−1h(ν)<d​⨁​Mdimψν​(C).

When det⁡Q(α)≠0\det Q(\alpha)\ne0detQ(α)=0, the U(α)U(\alpha)U(α) summand has order (n−1)wα(n-1)w^\alpha(n−1)wα. The goal also includes the multiplication law for the uuu operators, with coefficient Qjkbp(α)Q^{bp}_{jk}(\alpha)Qjkbp​(α) as in equation (6) of Proposition 44. This identity specifies how their natural generators multiply even when Q(α)Q(\alpha)Q(α) is singular. The two cases for SSS printed in Theorem 30, d≥nd\ge nd≥n and d<nd<nd<n, give the same uniform restriction h(ν)<dh(\nu)<dh(ν)<d because every partition of n−1n-1n−1 has at most n−1n-1n−1 rows.

Significance

The theorem identifies the simple ideals and their sizes from representation data of two smaller symmetric groups. It separates the dimension-dependent part MMM, where the rank of Q(α)Q(\alpha)Q(α) may drop, from the part SSS controlled by partitions with fewer than ddd rows. Consequently, it determines the irreducible representations of this concrete operator algebra and explains why its decomposition changes with ddd.

The result is proved in the cited paper; this mission asks for a machine-checked proof of its precise statement. The published operator model and tensor-permutation definition already fix the underlying matrices. A completed development would add reusable facts about partial transposition, ideals of represented group algebras, matrix units arising from singular coefficient matrices, and occurrence of symmetric-group representations. The read side of this mission is an open theorem, not a claim that Theorem 30 has already been formalized.

Difficulty

The natural spanning elements V(σ)tnV(\sigma)^{t_n}V(σ)tn​ are not a basis when d<nd<nd<n, and the uijab(α)u^{ab}_{ij}(\alpha)uijab​(α) can also be dependent. Counting generators therefore cannot establish the orders of the matrix ideals. The matrix Q(α)Q(\alpha)Q(α) records those dependencies; its rank, not its number of rows, governs the U(α)U(\alpha)U(α) summand. The complementary ideal SSS requires tracking which representations of S(n−1)S(n-1)S(n−1) survive after the MMM component is removed. A dimension count alone would identify neither the actual ideals nor their matrix-unit multiplication laws.

Formalization scope

Operators are matrices indexed by functions Fin n → Fin d, a coordinate model of (Cd)⊗n(\mathbb C^d)^{\otimes n}(Cd)⊗n. The last-factor transpose is the published ptLast; AAA and MMM are the published complex spans algA and algM. The paper's labels 1,…,n−11,\ldots,n-11,…,n−1 become Fin (m+1), and its last label becomes Fin.last (m+1). Permutations multiply right to left. The irreducible family is represented by real orthogonal matrices, hence by unitary complex matrices after casting; the explicit completeness condition ∑α(wα)2=(n−2)!\sum_\alpha(w^\alpha)^2=(n-2)!∑α​(wα)2=(n−2)! ensures that every irreducible of S(n−2)S(n-2)S(n−2) is present in the family.

Occurrence means that a nonzero intertwiner embeds an irreducible into the action on exactly (Cd)⊗(n−2)(\mathbb C^d)^{\otimes(n-2)}(Cd)⊗(n−2). An ideal is a complex subspace of AAA closed under multiplication on both sides. An assertion I≅Mr(C)I\cong M_r(\mathbb C)I≅Mr​(C) requires r2r^2r2 linearly independent matrix units spanning III and obeying the matrix-unit law; it cannot be discharged by a dimension count. For r=0r=0r=0 this requires I=0I=0I=0. The order dim⁡ψν\dim\psi^\nudimψν is represented by the number of standard Young tableaux of shape ν\nuν, using the classical symmetric-group dimension formula. The goal permits n=2n=2n=2 and requires d≥1d\ge1d≥1.

Theorem 30's displayed coefficient QikbpQ^{bp}_{ik}Qikbp​ conflicts with Proposition 44's equation (6), QjkbpQ^{bp}_{jk}Qjkbp​; the latter agrees with the matrix-index contraction and is used here. Contributions toward the listed source results, the partition occurrence criterion, and the singular-matrix algebra reduction are useful. An arbitrary family of subspaces with the right dimensions does not meet the target: the statements fix AAA, MMM, U(α)U(\alpha)U(α), Q(α)Q(\alpha)Q(α), and the matrix-unit structure of each component.

Selected references

  • M. Mozrzymas, M. Horodecki, M. Studziński, Structure and properties of the algebra of partially transposed permutation operators, Journal of Mathematical Physics 55, 032202 (2014), arXiv:1308.2653v3. The cited version supplies the page and result numbers used in this mission.
  • M. Studziński, M. Horodecki, M. Mozrzymas, Commutant structure of U⊗(n−1)⊗U transformations*, arXiv:1305.6183v2. Its published operator model supplies the shared Lean definitions.
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ProbabilityQuantum InformationTheoretical Computer Science·Captain: mikedeng1

Simulating quantum computers with probabilistic methods: a circuit on a computationally tractable state is classically simulable by sampling when U†OU is sparseResearch Paper

Why this problem arose

A quantum circuit may create a state whose full list of amplitudes is far too large for a classical computer to store. That fact alone does not show that every observable feature of its output is hard to estimate. In Simulating quantum computers with probabilistic methods, Van den Nest asks when classical sampling can reproduce the accuracy of a quantum experiment that estimates an observable's expectation. The paper's Theorem 1 identifies a condition on the input state and on the observable after it is pulled back through the circuit, rather than requiring the circuit itself to have a sparse matrix. This separates the cost of describing a whole output state from the cost of estimating the particular quantity measured at the end. Van den Nest, §§1–3

The paper distinguishes weak simulation, which achieves the accuracy available from polynomially many experimental runs, from strong simulation, which asks for much finer numerical precision. This mission addresses the sampling estimate behind the former. The source's 2010 preprint proves an efficient classical algorithm under computational assumptions; the formal target below states its finite probability guarantee for the particular estimator in that proof. Van den Nest, pp. 2, 6–7

States, sparse operators, and samples

An nnn-qubit computational basis has labels x∈{0,1}nx\in\{0,1\}^nx∈{0,1}n. A state ∣ψ⟩|\psi\rangle∣ψ⟩ has complex coefficient ψx=⟨x∣ψ⟩\psi_x=\langle x|\psi\rangleψx​=⟨x∣ψ⟩ at each label, with ∑x∣ψx∣2=1\sum_x|\psi_x|^2=1∑x​∣ψx​∣2=1. Measurement in this basis yields xxx with Born probability px=∣ψx∣2p_x=|\psi_x|^2px​=∣ψx​∣2. A state is computationally tractable (CT) in the paper when these probabilities can be sampled, and individual coefficients can be evaluated, in polynomial time. The finite development below represents the resulting sample and coefficient access directly. Van den Nest, Definition 1, p. 8

For a matrix AAA, the entry AyxA_{yx}Ayx​ is its transition from basis label xxx to label yyy. The operator is sss-sparse if each row and each column has at most sss nonzero entries. Its column data consist of coefficients αi(x)\alpha_i(x)αi​(x) and row labels ri(x)r_i(x)ri​(x) for i=1,…,si=1,\ldots,si=1,…,s, with A∣x⟩=∑iαi(x)∣ri(x)⟩A|x\rangle=\sum_i\alpha_i(x)|r_i(x)\rangleA∣x⟩=∑i​αi​(x)∣ri​(x)⟩. Nonzero coefficients in a column occupy distinct rows. The paper calls such an operator efficiently computable sparse (ECS) when the nonzero entries can also be found efficiently. Van den Nest, §4.3, pp. 10–11

For two normalized states ψ,ϕ\psi,\phiψ,ϕ, write qy=∣ϕy∣2q_y=|\phi_y|^2qy​=∣ϕy​∣2. The paper defines bounded complex functions FiF_iFi​ and GiG_iGi​ from the column data, separating each contribution according to whether px≥qri(x)p_x\ge q_{r_i(x)}px​≥qri​(x)​. The estimator is the sum over iii of a sample mean of FiF_iFi​ under ppp and a sample mean of GiG_iGi​ under qqq. The same KKK independent draws from each law are used for every iii in this formalization. Its target is the matrix element ⟨ϕ∣A∣ψ⟩\langle\phi|A|\psi\rangle⟨ϕ∣A∣ψ⟩. Van den Nest, Eqs. (5)–(8), pp. 12–13

Formalization targets

The main result concerns a unitary UUU, a Hermitian observable OOO with spectral norm at most one, and the pulled-back operator B=U†OUB=U^\dagger O UB=U†OU. When BBB is sss-sparse and has the stated column data, the estimator o^\widehat oo targets the output expectation ⟨Uψ∣O∣Uψ⟩\langle U\psi|O|U\psi\rangle⟨Uψ∣O∣Uψ⟩. For K≥1K\ge1K≥1 samples of each kind and ε>0\varepsilon>0ε>0, the target is

Pr⁡{∣o^−⟨Uψ∣O∣Uψ⟩∣>ε}≤8sexp⁡(−Kε232s4).\Pr\bigl\{|\widehat o-\langle U\psi|O|U\psi\rangle|>\varepsilon\bigr\} \le 8s\exp\left(-\frac{K\varepsilon^2}{32s^4}\right).Pr{∣o−⟨Uψ∣O∣Uψ⟩∣>ε}≤8sexp(−32s4Kε2​).

The paper states Theorem 1 as an efficient simulation claim. The displayed explicit tail is obtained from its Theorem 3, the pointwise bounds on FiF_iFi​ and GiG_iGi​, and Appendix A's Chernoff–Hoeffding estimate. Its exact constants are a commitment of this finite accuracy target, not a constant printed in Theorem 1. Van den Nest, Theorem 1, p. 2; Theorem 3, p. 11; Eq. (18), p. 23

The milestones follow the paper's supporting statements: the real and complex sampling bounds, the sparse matrix-element decomposition, the two expectation identities, the bound on FiF_iFi​, the row-preimage count, the bound on GiG_iGi​, and the general matrix-element estimate of Theorem 3. Theorem 3 permits two different normalized states and a sparse operator that need not be unitary. Its specialization with ϕ=ψ\phi=\psiϕ=ψ and A=U†OUA=U^\dagger O UA=U†OU gives the target above. Van den Nest, pp. 11–13, 23

What the result provides

The theorem gives a concrete error probability for recovering an output observable's expectation from classical samples of the input state. The condition concerns U†OUU^\dagger O UU†OU; it allows the circuit matrix UUU itself to be dense. Thus it applies to circuit and observable pairs for which output-state enumeration is a poor guide to the cost of this particular expectation estimate. The paper develops consequences for local observables and other circuit families after Theorem 3. Van den Nest, Theorem 1 and §5

A formal development would make the finite probability claim, the sample-access model, and the spectral-norm assumptions independently checkable. The paper's theorem is proved mathematically, but this mission's Lean theorems are open statements awaiting proofs. In particular, machine-checking the explicit estimator's accuracy is separate from representing a polynomial-time classical machine, which this mission does not undertake.

Where the difficulty lies

Sparse columns make ⟨ϕ∣A∣ψ⟩\langle\phi|A|\psi\rangle⟨ϕ∣A∣ψ⟩ a sum of terms indexed by iii, but they do not by themselves give a bounded random variable when a term is sampled from pxp_xpx​. Dividing by a small pxp_xpx​ may create a large weight. Sampling from qyq_yqy​ has the analogous problem in the opposite direction, and the row labels ri(x)r_i(x)ri​(x) need not be injective as functions of xxx. The paper's two functions split those regimes; its row-sparsity condition controls the number of terms that can contribute to one Gi(y)G_i(y)Gi​(y). The proof must also keep the complex modulus, the strict failure event, and the shared sample sets consistent with the finite probability law. Van den Nest, proof of Theorem 3, pp. 12–13

Formalization scope

Lean represents basis labels as functions Fin n → Bool, states as finite complex coefficient vectors, and operators as complex matrices. The operator bound uses the published spectral norm QAlgorithms.specNorm. Theorem 1 assumes a unit vector, a unitary matrix, and a Hermitian observable of norm at most one. The general Theorem 3 uses any finite basis and two normalized coefficient vectors. Column data can enumerate nonzero entries in any order; the proof needs their values and distinctness, while the paper fixes top-to-bottom order. All expectations and event probabilities are finite sums. No measurable-space conventions or Bochner-integral defaults enter.

The estimator is fixed by the definitions of FiF_iFi​, GiG_iGi​, and their two sample means. It reads sampled labels, state coefficients, and sparse column data. It cannot read the target matrix element, enumerate all basis labels to output the answer, or inspect UUU and OOO outside the supplied column data. The model asserts the accuracy that these accesses support; it does not certify that sampling, coefficient evaluation, column enumeration, or the circuit family run in polynomial time. This is the precise part of the paper's classical simulation statement represented here.

Positive KKK avoids the undefined statistical meaning of an empty sample mean. The split assigns equality px=qri(x)p_x=q_{r_i(x)}px​=qri​(x)​ to FiF_iFi​. A zero Born probability has zero sampling mass; the corresponding totalized quotient is set to zero. For s=0s=0s=0, the sparse matrix and estimator are zero, and the theorem's failure bound is zero. The displayed 8s8s8s bound is the one derived from the paper's inequalities; the complex-valued intermediate constant is likewise derived from Eq. (18). Reusable contributions include the finite product-sampling concentration theorem, the column-data representation, and the matrix-element decomposition. Van den Nest, pp. 10–13, 23

Selected references

  • M. Van den Nest, Simulating quantum computers with probabilistic methods, arXiv:0911.1624v3, 2010. arXiv
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CombinatoricsQuantum InformationRepresentation Theory·Captain: mikedeng1

Optimal Quantum Purity Amplification: Removing the Bottom Box of the Last Column of Each Schur-Sampled Young Diagram Gives the Optimal Choi Matrix for Purifying n Depolarized QuditsResearch Paper

Motivation

Quantum devices rarely prepare the state they are asked for. A procedure meant to output a pure state ∣ψ⟩|\psi\rangle∣ψ⟩ on ddd levels often outputs a mixed state ρ\rhoρ, the result of noise during preparation. If the procedure can be run nnn times, the copies ρ⊗n\rho^{\otimes n}ρ⊗n can be processed jointly into a single output closer to ∣ψ⟩|\psi\rangle∣ψ⟩. This task is quantum purity amplification (QPA), also called purification. It appears as a primitive in error mitigation, in state preparation on near-term hardware, and in the theory of quantum state estimation and cloning.

For qubits and depolarizing noise, Cirac, Ekert and Macchiavello found the optimal protocol in 1999 (Phys. Rev. Lett. 82, 4344), and Keyl and Werner determined the rate of optimal purification procedures (Ann. Henri Poincaré 2, 2001), with the minimum fidelity as figure of merit. For qudits (d>2d>2d>2) the optimal protocol remained open. Childs, Fu, Leung, Li, Ozols and Vyas gave a streaming protocol (arXiv:2309.16387), and Grinko and Ozols reduced unitary-equivariant SDPs of this type to linear programs (arXiv:2207.05713) without solving this one in closed form. Li, Fu, Isogawa, Silva and Chuang (arXiv:2409.18167, version 4 of 25 Dec 2025) solve the qudit case exactly: they give the Choi matrix of the optimal channel in closed form (Theorem II.1).

Setting

Let W=CdW=\mathbb C^dW=Cd. An unknown pure state σ=∣ψ⟩⟨ψ∣\sigma=|\psi\rangle\langle\psi|σ=∣ψ⟩⟨ψ∣ is corrupted by the depolarizing channel of strength λ∈(0,1)\lambda\in(0,1)λ∈(0,1):

ρ=Dλ(σ)=(1−λ) σ+λ Idd.\rho=\mathcal D_\lambda(\sigma)=(1-\lambda)\,\sigma+\lambda\,\frac{\mathbb I_d}{d}.ρ=Dλ​(σ)=(1−λ)σ+λdId​​.

A QPA protocol is a quantum channel Φ\PhiΦ from W⊗nW^{\otimes n}W⊗n (the input registers) to WWW (the output register). Its quality at ψ\psiψ is the fidelity FΦ(ψ)=⟨ψ∣Φ(ρ⊗n)∣ψ⟩F_\Phi(\psi)=\langle\psi|\Phi(\rho^{\otimes n})|\psi\rangleFΦ​(ψ)=⟨ψ∣Φ(ρ⊗n)∣ψ⟩, and the figure of merit is the minimum fidelity min⁡∥ψ∥=1FΦ(ψ)\min_{\|\psi\|=1}F_\Phi(\psi)min∥ψ∥=1​FΦ​(ψ).

A channel is described by its Choi matrix TTT, an operator on out⊗in\mathrm{out}\otimes\mathrm{in}out⊗in with T⪰0T\succeq0T⪰0 and troutT=Iin\mathrm{tr}_{\mathrm{out}}T=\mathbb I_{\mathrm{in}}trout​T=Iin​; the channel is ΦT(X)=trin(T(I⊗X⊤))\Phi_T(X)=\mathrm{tr}_{\mathrm{in}}(T(\mathbb I\otimes X^\top))ΦT​(X)=trin​(T(I⊗X⊤)). Averaging the fidelity over a Haar-random ψ\psiψ gives the semidefinite program (SDP)

max⁡ tr(C⊤T)s.t.troutT=Iin, T⪰0,C=∫σU⊤⊗ρU⊗n dU,\max\ \mathrm{tr}(C^\top T)\quad\text{s.t.}\quad \mathrm{tr}_{\mathrm{out}}T=\mathbb I_{\mathrm{in}},\ T\succeq0,\qquad C=\int\sigma_U^\top\otimes\rho_U^{\otimes n}\,dU,max tr(C⊤T)s.t.trout​T=Iin​, T⪰0,C=∫σU⊤​⊗ρU⊗n​dU,

with σU=U∣0⟩⟨0∣U†\sigma_U=U|0\rangle\langle0|U^\daggerσU​=U∣0⟩⟨0∣U†, ρU=Dλ(σU)\rho_U=\mathcal D_\lambda(\sigma_U)ρU​=Dλ​(σU​), and dUdUdU the Haar probability measure on U(d)U(d)U(d).

The answer is phrased with Young diagrams. A Young diagram ς\varsigmaς with nnn boxes and at most ddd rows labels an irreducible representation W[ς]W^{[\varsigma]}W[ς] of U(d)U(d)U(d) of dimension d[ς]d^{[\varsigma]}d[ς], and Πς\Pi_\varsigmaΠς​ denotes the projector onto the ς\varsigmaς-isotypic part of W⊗nW^{\otimes n}W⊗n (weak Schur sampling). The protocol must be covariant under the mixed representation R(U)=Uˉ⊗U⊗nR(U)=\bar U\otimes U^{\otimes n}R(U)=Uˉ⊗U⊗n. Inside the ς\varsigmaς-sector this representation splits as ⨁iW[μi]\bigoplus_i W^{[\mu_i]}⨁i​W[μi​], where [μi]=ς−ei[\mu_i]=\varsigma-e_i[μi​]=ς−ei​ removes the last box of row iii of ς\varsigmaς (padded with zeros to ddd rows). Row iii is feasible if it is the last row or ςi>ςi+1\varsigma_i>\varsigma_{i+1}ςi​>ςi+1​. Let i∗i^*i∗ be the smallest feasible row; [μi∗][\mu_{i^*}][μi∗​] is ς\varsigmaς with the bottom box of its last column removed. PμP_\muPμ​ is the projector onto the [μ][\mu][μ]-isotypic component of RRR.

Formalization targets

Goal: Theorem II.1

T∗=∑ςd[ς]d[μi∗]  Pμi∗(Iout⊗Πς)T^*=\sum_{\varsigma}\frac{d^{[\varsigma]}}{d^{[\mu_{i^*}]}}\;P_{\mu_{i^*}}\big(\mathbb I_{\mathrm{out}}\otimes\Pi_\varsigma\big)T∗=ς∑​d[μi∗​]d[ς]​Pμi∗​​(Iout​⊗Πς​)

is feasible and optimal for the SDP. Its channel ΦT∗\Phi_{T^*}ΦT∗​ is a quantum channel. For every channel Φ\PhiΦ, min⁡ψFΦ(ψ)≤min⁡ψ′FΦT∗(ψ′)\min_\psi F_\Phi(\psi)\le\min_{\psi'}F_{\Phi_{T^*}}(\psi')minψ​FΦ​(ψ)≤minψ′​FΦT∗​​(ψ′). The statement asserts optimality, not uniqueness, and holds for every d≥1d\ge1d≥1, n≥0n\ge0n≥0, 0<λ<10<\lambda<10<λ<1.

Milestones (in the order the proof uses them)

  • Proposition S2.1. An operator commuting with Uˉ⊗U⊗n\bar U\otimes U^{\otimes n}Uˉ⊗U⊗n (U∈SU(d)U\in SU(d)U∈SU(d)) and with input permutations is a scalar mim_imi​ on each block [μi][\mu_i][μi​] of every sector.
  • Eq. (S23). ∣ψ⟩⟨ψ∣=A(−ρ−1)+B Id/d|\psi\rangle\langle\psi|=A(-\rho^{-1})+B\,\mathbb I_d/d∣ψ⟩⟨ψ∣=A(−ρ−1)+BId​/d with A=λ(d(1−λ)+λ)d2(1−λ)A=\frac{\lambda(d(1-\lambda)+\lambda)}{d^2(1-\lambda)}A=d2(1−λ)λ(d(1−λ)+λ)​, B=d+λ1−λB=d+\frac{\lambda}{1-\lambda}B=d+1−λλ​.
  • Lemma S2.3. P=Id−Id⊗troutP=\mathrm{Id}-\frac{\mathbb I}{d}\otimes\mathrm{tr}_{\mathrm{out}}P=Id−dI​⊗trout​ is an orthogonal projector.
  • Lemma S2.4. If P(C1)=AP(C2)P(C_1)=AP(C_2)P(C1​)=AP(C2​) with A>0A>0A>0, the two SDPs have the same optimal solutions.
  • Eq. (S25). P(C)=AP(C′)P(C)=AP(C')P(C)=AP(C′) with C′=−∫(ρU⊤)−1⊗ρU⊗n dUC'=-\int(\rho_U^\top)^{-1}\otimes\rho_U^{\otimes n}\,dUC′=−∫(ρU⊤​)−1⊗ρU⊗n​dU.
  • Eq. (S26). C′C'C′ acts on the block [μi][\mu_i][μi​] as ci′=−S[μi](a,…,a,b)c'_i=-S^{[\mu_i]}(a,\dots,a,b)ci′​=−S[μi​](a,…,a,b), a=λ/da=\lambda/da=λ/d, b=1−d−1dλb=1-\frac{d-1}{d}\lambdab=1−dd−1​λ, where S[μ]=s[μ]/d[μ]S^{[\mu]}=s^{[\mu]}/d^{[\mu]}S[μ]=s[μ]/d[μ] is the normalized Schur polynomial.
  • Eqs. (S27)–(S28). S[μ]≤S[λ]S^{[\mu]}\le S^{[\lambda]}S[μ]≤S[λ] on (0,∞)d(0,\infty)^d(0,∞)d iff [μ]⪯[λ][\mu]\preceq[\lambda][μ]⪯[λ] in dominance order.
  • p. 21. [μi]⪯[μj][\mu_i]\preceq[\mu_j][μi​]⪯[μj​] whenever i≤ji\le ji≤j.

Significance

The theorem gives the exact optimal purification channel for every ddd, nnn and depolarizing strength, and the channel does not depend on λ\lambdaλ. It has an operational form, worked out in the paper's Sec. II C: Schur sampling, a correction inside each sector, and a partial trace. From it the paper derives the optimal sample complexity n≈1δ(1−1d)λ(1−λ)2n\approx\frac1\delta(1-\frac1d)\frac{\lambda}{(1-\lambda)^2}n≈δ1​(1−d1​)(1−λ)2λ​ for output infidelity δ\deltaδ (Theorem II.2) and an efficient circuit implementation (Algorithm 1). Both rest on Theorem II.1.

The result is proved on paper but not formalized anywhere. A formal proof would check a chain that mixes semidefinite programming, Haar integration, the Schur–Weyl duality of the mixed representation Uˉ⊗U⊗n\bar U\otimes U^{\otimes n}Uˉ⊗U⊗n, and a combinatorial inequality for normalized Schur polynomials (Sra's theorem, European J. Combin. 51, 2016), which is cited and not proved in the paper. Several of these components are general results: the block decomposition of covariant operators, the cost-matrix projection argument for SDPs with a partial-trace constraint, and the dominance ordering of normalized Schur polynomials.

Difficulty

Symmetry reduces the SDP to a linear program in one coefficient tit_iti​ per block, but the coefficients cic_ici​ of the original cost matrix CCC are hard to evaluate directly. The proof replaces CCC by C′C'C′, whose block coefficients are characters of rational representations evaluated at the spectrum of ρ\rhoρ, and shows that the replacement leaves the optimizer unchanged. The remaining step compares these characters across blocks. That comparison is the Cuttler–Greene–Skandera inequality for normalized Schur polynomials, a nontrivial combinatorial theorem. One natural guess fails: keeping the block of the largest feasible row instead of the smallest gives a channel that is not optimal in general. The optimal block removes the bottom box of the last column, which is generally a different row.

Formalization scope

Operators are complex matrices indexed by Fin d×(Fin n→Fin d)\mathrm{Fin}\,d\times(\mathrm{Fin}\,n\to\mathrm{Fin}\,d)Find×(Finn→Find), output register first. Partial traces are the published WildeQIT.partialTraceLeft/Right. The Haar measure is the published probability Haar measure QAlgorithms.Schur.unitaryHaar d on U(d)U(d)U(d), and Haar integrals of matrices are taken entrywise. Young diagrams, Schur polynomials, dimensions d[ν]d^{[\nu]}d[ν] (semistandard tableau counts), Schur modules with their polynomial representations, and the weak Schur sampling projector Πς\Pi_\varsigmaΠς​ come from the published QAlgorithms.Schur layer; channels are QAlgorithms.IsChannel (finite Kraus families). Rows are 0-based in Lean.

The irreps [μi][\mu_i][μi​] of the mixed representation (Nguyen, arXiv:2310.01613) are rational: when ς\varsigmaς has fewer than ddd rows, μd\mu_dμd​ has last row −1-1−1. They are encoded by the determinant shift νi=ς+(1d)−ei\nu_i=\varsigma+(1^d)-e_iνi​=ς+(1d)−ei​, a Young diagram with n+d−1n+d-1n+d−1 boxes, with [μi]=[νi]⊗det⁡−1[\mu_i]=[\nu_i]\otimes\det^{-1}[μi​]=[νi​]⊗det−1. The isotypic projector is the character integral Pμ=d[ν]∫χν(U)‾det⁡U R(U) dUP_\mu=d^{[\nu]}\int\overline{\chi_\nu(U)}\det U\,R(U)\,dUPμ​=d[ν]∫χν​(U)​detUR(U)dU.

Disclosed choices:

  • Proposition S2.1 is stated on the full space with an added permutation-invariance hypothesis, which replaces the paper's restriction to one irrep block. Without it the full-space statement is false.
  • Lemma S2.4 uses Re tr(CT)\mathrm{Re}\,\mathrm{tr}(CT)Retr(CT) without the transpose, as printed, and the constraint troutT=I\mathrm{tr}_{\mathrm{out}}T=\mathbb Itrout​T=I.
  • Eq. (S28) makes the quantifier over positive arguments explicit.
  • The goal's minimum-fidelity clause is stated without infima: there is a ψ\psiψ whose fidelity under Φ\PhiΦ is at most the fidelity of ΦT∗\Phi_{T^*}ΦT∗​ at every ψ′\psi'ψ′.

Trivializing formalizations are ruled out. T∗T^*T∗ is the explicit operator above, computed from ddd and nnn alone, never an argmax or a hypothesis. The cost matrix is the actual Haar integral, not a closed form. The competitors are all feasible TTT and all channels Φ\PhiΦ, with no symmetry assumed.

Welcome contributions: the tracing and Pieri-type decomposition of Uˉ⊗U⊗n\bar U\otimes U^{\otimes n}Uˉ⊗U⊗n; Haar orthogonality of characters on U(d)U(d)U(d); the equivalence of Choi feasibility and Kraus channels; Sra's inequality. Each is reusable beyond this mission.

Selected references

  • Z. Li, H. Fu, T. Isogawa, C. Silva, I. Chuang, Optimal Quantum Purity Amplification, arXiv:2409.18167v4, 2025. https://arxiv.org/abs/2409.18167
  • J. I. Cirac, A. K. Ekert, C. Macchiavello, Optimal purification of single qubits, Phys. Rev. Lett. 82, 4344, 1999. https://doi.org/10.1103/PhysRevLett.82.4344
  • M. Keyl, R. F. Werner, The rate of optimal purification procedures, Annales Henri Poincaré 2, 1–26, 2001.
  • A. M. Childs, H. Fu, D. Leung, Z. Li, M. Ozols, V. Vyas, Streaming quantum state purification, arXiv:2309.16387, 2023. https://arxiv.org/abs/2309.16387
  • D. Grinko, M. Ozols, Linear programming with unitary-equivariant constraints, arXiv:2207.05713, 2023. https://arxiv.org/abs/2207.05713
  • Q. T. Nguyen, The mixed Schur transform: efficient quantum circuit and applications, arXiv:2310.01613, 2023. https://arxiv.org/abs/2310.01613
  • S. Sra, On inequalities for normalized Schur functions, European Journal of Combinatorics 51, 492, 2016.
15 thms3 active usersReviewed
Information TheoryMathematical PhysicsQuantum Information·Captain: mikedeng1

The Entropy Photon-Number Inequality and its Consequences: It Implies Both Minimum Output Entropy Conjectures, So Vacuum and Thermal Inputs Minimize the Beam-Splitter Output EntropyResearch Paper

Motivation

Light carries information in electromagnetic field modes. At optical frequencies, photon statistics affect the capacities of thermal-noise and broadcast communication channels. Bounds on these capacities depend on identifying the smallest entropy that a beam splitter can produce under specified input conditions. Guha, Erkmen, and Shapiro explain why two such minimum output entropy claims matter: their first supports the proposed thermal-noise channel capacity, and their second supports the proposed bosonic broadcast capacity region. The paper states both as conjectures and shows that they follow from its Entropy Photon-Number Inequality (EPnI).

The authors model the EPnI on the classical entropy power inequality, but its quantum version concerns density operators rather than probability densities. Their 2007 paper does not prove the EPnI. A later platform theorem, sourced from an OpenAI mathematics preprint codebase, is marked Proved for finite-energy inputs. It supplies this mission's referenced first milestone. The statements here express the paper's two consequences in that same model; their Lean proofs are still open in this proposal.

Setting

A bosonic mode has number states ∣m⟩|m\rangle∣m⟩ indexed by m∈Nm\in\mathbb Nm∈N. An nnn-mode state ρ\rhoρ is a positive density operator on the full Fock space indexed by Nn\mathbb N^nNn, with trace one. Its von Neumann entropy is S(ρ)=−tr⁡(ρlog⁡ρ)S(\rho)=-\operatorname{tr}(\rho\log\rho)S(ρ)=−tr(ρlogρ). All logarithms are natural. A thermal state with average photon number N≥0N\ge0N≥0 per mode has weights Nm/(N+1)m+1N^m/(N+1)^{m+1}Nm/(N+1)m+1 in the number basis; for nnn modes the state is the product of these single-mode distributions. At N=0N=0N=0 this is the vacuum, with zero photons in every mode. A pure state is a projector onto a unit Fock vector. A state has zero mean field when the expectation of the annihilation operator is zero for each mode.

Two independent input states ρa\rho_aρa​ and ρb\rho_bρb​ enter a lossless beam splitter with transmissivity η∈[0,1]\eta\in[0,1]η∈[0,1]. For each mode its retained output has annihilation operator c^=η a^+1−η b^\hat c=\sqrt{\eta}\,\hat a+\sqrt{1-\eta}\,\hat bc^=η​a^+1−η​b^; the other output is discarded. The retained density operator is ρc\rho_cρc​. Independence means that the joint input is ρa⊗ρb\rho_a\otimes\rho_bρa​⊗ρb​; correlations among modes inside either input are allowed. The thermal entropy per mode is

g(N)=(N+1)log⁡(N+1)−Nlog⁡N,g(N)=(N+1)\log(N+1)-N\log N,g(N)=(N+1)log(N+1)−NlogN,

with the continuous convention at N=0N=0N=0. The entropy photon-number of an nnn-mode state is g−1(S(ρ)/n)g^{-1}(S(\rho)/n)g−1(S(ρ)/n). Eq. (13) of the paper asserts that the output entropy photon-number is at least η\etaη times that of the first input plus 1−η1-\eta1−η times that of the second. The source paper gives the definitions in §II.B, p. 2.

Formalization targets

The first target fixes the second input to a thermal product state of mean K≥0K\ge0K≥0, while the first ranges over zero-mean-field pure states. The second fixes the first input to the vacuum, while the second ranges over states with entropy ng(K)n g(K)ng(K). For each class, the claimed lower bound and attained minimum are

S(ρc)≥n g((1−η)K),min⁡S(ρc)=n g((1−η)K).S(\rho_c)\ge n\,g((1-\eta)K),\qquad \min S(\rho_c)=n\,g((1-\eta)K).S(ρc​)≥ng((1−η)K),minS(ρc​)=ng((1−η)K).

For the first class the vacuum first input attains equality. For the second, the product thermal second input attains equality. The goal states both claims together, including the existence of an attaining input and output. The shared attack path contains the EPnI, Eq. (13), the scalar properties of ggg and its inverse, thermal state existence and entropy, zero entropy of pure states, the beam splitter's thermal output for vacuum and thermal inputs, and the inequalities of Eqs. (16)–(17). Each milestone uses the statement on pp. 2–3 of the paper.

Significance

An attained minimum gives the precise noise floor for the two input classes. In the paper's capacity arguments, the first class concerns the thermal-noise channel and the second the bosonic broadcast channel. The mission records the exact optimizer and the output entropy, including the endpoints η=0,1\eta=0,1η=0,1 and K=0K=0K=0. Without the optimizer's output value, a lower bound alone would not identify the minimum.

The referenced EPnI is marked Proved on Prove2Me under finite-energy assumptions. This mission's thermal-state, pure-state, and beam-splitter statements are draft targets and have no machine-checked proofs here. Closing them would connect the platform's general inequality to the two applications explicitly worked through by Guha, Erkmen, and Shapiro. The thermal-state and entropy facts can also serve other bosonic-channel formalizations using the same Fock-space interface.

Difficulty

The EPnI supplies an entropy photon-number bound, but converting it into an attained output-entropy minimum requires more than substituting a pure input. One must justify that the inverse thermal entropy behaves as expected on nonnegative entropies, that thermal product states really exist in the chosen infinite-dimensional state space, and that vacuum mixed with thermal noise produces the specified thermal output. The last claim is a statement about the full beam-splitter matrix and its partial trace, not just a scalar entropy comparison. Infinite sums also demand care: a formal expression that defaults to zero when it diverges would give a spurious entropy value.

Formalization scope

The development reuses OAI.EntropyPhotonNumber.State n, its number-basis matrix entries, real-valued entropy, ggg, the infimum definition of g−1g^{-1}g−1, and the beam-splitter output relation. The new definitions express thermal, vacuum, pure, and zero-mean-field states on that same carrier. The thermal state uses Eq. (10)'s number-basis formula; Eq. (9)'s coherent-state integral is outside this mission. The beam splitter uses the sign convention in the published definition, which yields the paper's retained output c^\hat cc^. The zero-mean-field condition includes convergence of each annihilation expectation.

There is at least one mode, n≥1n\ge1n≥1, since Eq. (11) divides entropy by nnn. Inputs to which the EPnI is applied have finite energy. This assumption is additional to the paper's phrasing: it is required by the referenced platform theorem and prevents the real-valued infinite-series entropy from taking a default zero on a divergent input. The first optimized input is therefore a finite-energy pure state; the second is a finite-energy state of entropy ng(K)n g(K)ng(K). The thermal and vacuum witnesses themselves have finite energy. These conditions are disclosed in the theorem statements and are not assertions that the unrestricted conjectures have been settled here.

The goal quantifies over every feasible input and corresponding output, states equality for every output from the named optimizer, and asserts that the optimizer and an output exist. This rules out a vacuous result from an empty thermal-state class or a bound that omits attainment. Contributions to the scalar ggg lemmas, thermal-state construction, pure-state entropy, and the beam-splitter output calculation are all within scope. Infrastructure for summable Fock-space matrix entries and operator entropy should remain reusable beyond this mission.

Selected references

  • S. Guha, B. I. Erkmen, and J. H. Shapiro, The Entropy Photon-Number Inequality and its Consequences, arXiv:0710.5666v2, 2007. arXiv
  • OpenAI, EntropyPhotonNumber Lean development, September 2026, unreviewed preprint code. Source; Prove2Me theorem.
11 thms3 active usersReviewed
AlgebraRepresentation Theory·Captain: mikedeng1

Cyclotomic Birman–Wenzl–Murakami Algebras, II: Admissibility Relations and Freeness: Over an Admissible Integral Domain S, W_{n,S,r} Is a Free S-Module of Rank r^n(2n−1)!!Research Paper

Motivation

The cyclotomic Birman–Wenzl–Murakami algebra is an algebra of braids and contractions equipped with an additional cyclotomic relation. It connects diagram algebras, representation theory, and knot theoretic constructions. For calculations over a coefficient ring, one needs to know whether the diagrammatic spanning elements remain independent after parameters are specialized. The freeness theorem of Goodman and Hauschild Mosley answers that question for admissible integral ground rings: the algebra has a basis of the size predicted by labeled Brauer diagrams. The paper also identifies the algebra with a cyclotomic Kauffman tangle algebra. This mission targets the algebra's freeness and rank assertion.

The cited paper builds on admissibility relations developed with Wilcox and Yu. Its earlier definitions and preliminary statements already appear in Prove2Me mission 92e1197e-907f-4ab8-92be-01ea44f6cfef. The present mission reuses that published layer and poses the deferred freeness theorem and the intermediate results that support it. The distinction matters because two algebras with similar names but different generators or parameter conventions need not have the same rank statement.

Setting

A ground ring SSS is a commutative unital ring with a positive integer rrr and parameters ρ,q,δ0,δ1,…,u1,…,ur\rho,q,\delta_0,\delta_1,\ldots,u_1,\ldots,u_rρ,q,δ0​,δ1​,…,u1​,…,ur​. The parameters ρ,q,δ0,u1,…,ur\rho,q,\delta_0,u_1,\ldots,u_rρ,q,δ0​,u1​,…,ur​ are units, and they satisfy

ρ−1−ρ=(q−1−q)(δ0−1).\rho^{-1}-\rho=(q^{-1}-q)(\delta_0-1).ρ−1−ρ=(q−1−q)(δ0​−1).

The algebra Wn,S,rW_{n,S,r}Wn,S,r​ is generated over SSS by invertible braids gig_igi​, contractions eie_iei​, and an invertible affine generator y1y_1y1​. It obeys the affine BMW relations of Definition 2.1 and the cyclotomic relation ∏j=1r(y1−uj)=0\prod_{j=1}^r(y_1-u_j)=0∏j=1r​(y1​−uj​)=0 of Definition 2.8. The shared published presentation uses indices i=0,…,n−2i=0,\ldots,n-2i=0,…,n−2 for gig_igi​ and eie_iei​, corresponding to the paper's gi+1g_{i+1}gi+1​ and ei+1e_{i+1}ei+1​. At n=0n=0n=0 there are no generators.

The parameters are admissible when q−q−1q-q^{-1}q−q−1 is nonzero and not a zero divisor, weak admissibility holds for every integer shift of the δ\deltaδ relations, and e1,y1e1,…,y1r−1e1e_1,y_1e_1,\ldots,y_1^{r-1}e_1e1​,y1​e1​,…,y1r−1​e1​ are SSS-linearly independent in W2,S,rW_{2,S,r}W2,S,r​. These are the conditions of Definition 3.3, expressed using condition (1) of Theorem 3.2. A morphism of ground rings preserves all δj\delta_jδj​ and uiu_iui​ and permits exactly the four paired sign actions on ρ\rhoρ and qqq in Definition 2.13. Consequently, base change includes the sign twists allowed by the paper.

For the generic case, F=Q(q,u1,…,ur)F=\mathbb Q(q,u_1,\ldots,u_r)F=Q(q,u1​,…,ur​) is the rational function field in algebraically independent variables. Put p=∏jujp=\prod_j u_jp=∏j​uj​, set ρ=p\rho=pρ=p for odd rrr and ρ=q−1p\rho=q^{-1}pρ=q−1p for even rrr, and define δa=∑jγjuja\delta_a=\sum_j\gamma_j u_j^aδa​=∑j​γj​uja​, where γj\gamma_jγj​ is the rational expression in equation (3.6). A shape in Γn\Gamma_nΓn​ is an rrr-tuple of Young diagrams whose total number of boxes is at most nnn and congruent to nnn modulo two. An up–down tableau of shape λ\lambdaλ is a path from the empty tuple to λ\lambdaλ, adding or removing one box at each step. Its set is T(n,λ)T(n,\lambda)T(n,λ).

Formalization targets

The central target is the freeness half of Theorem 6.1. For every admissible integral ground ring SSS and every n≥0n\ge0n≥0,

Wn,S,r≅SS rn(2n−1)!!.W_{n,S,r}\cong_S S^{\,r^n(2n-1)!!}.Wn,S,r​≅S​Srn(2n−1)!!.

Here (−1)!!=1(-1)!!=1(−1)!!=1, so the asserted rank at n=0n=0n=0 is one. A basis indexed by a finite type of that cardinality states both freeness and rank.

The milestone path includes the paper's admissibility equivalences, generic parameter construction, universal admissible integral domain, base change, the spanning family of rn(2n−1)!!r^n(2n-1)!!rn(2n−1)!! elements, the relevant Jones ideal and Hecke quotient results, and the generic structure results. At the generic field, Theorem 4.8 supplies split matrix blocks indexed by Γn\Gamma_nΓn​, with block size ∣T(n,λ)∣|T(n,\lambda)|∣T(n,λ)∣. The count in the proof of Theorem 5.2 is

∑λ∈Γn∣T(n,λ)∣2=rn(2n−1)!!,\sum_{\lambda\in\Gamma_n}|T(n,\lambda)|^2=r^n(2n-1)!!,λ∈Γn​∑​∣T(n,λ)∣2=rn(2n−1)!!,

which agrees with the generic dimension asserted by Theorem 5.2. The final theorem applies over an admissible integral domain, rather than only over FFF.

Significance

The result supplies an exact finite basis for Wn,S,rW_{n,S,r}Wn,S,r​ throughout the admissible integral-domain regime. It fixes the module rank independently of a choice of specialization and gives a numerical benchmark for presentations and representations of these algebras. The generic matrix decomposition also records the simple-block labels and their sizes; the tableau identity explains how those dimensions total the same rank.

Goodman and Hauschild Mosley proved these results. This mission asks for machine-checked proofs of the statements already known in the paper. Its reusable output includes ground-ring morphisms with sign twists, the generic parameter model, and finite tableau types. The published preliminary layer in mission 92e1197e-907f-4ab8-92be-01ea44f6cfef contains two proved and four open results among the six referenced milestones; none of the eight new theorem statements is presented here as already machine proved.

Difficulty

A spanning family alone does not show a basis: specializations can introduce linear dependence, and an equality of dimensions over one field does not itself establish independence over every integral ground ring. The argument also has to maintain the exact admissibility conditions when moving between coefficient rings. Over the generic field, identifying the right semisimple blocks requires the branching shapes and tableau sizes, while the final statement concerns arbitrary admissible integral domains. These are distinct algebraic regimes, and the same presentation and parameter conventions must be kept through each one.

Formalization scope

Lean uses the published GroundParameters, BMW, BMWAdmissible, UAdmissible, and equation (3.6) gamma expression from QAlgorithms.Papers.Independent.Support21.P14. The algebra is the quotient of a free algebra by the source's relations, with zero-based generator indices. The new definition layer records all four sign cases of Definition 2.13, the generic field as a fraction ring of a multivariate polynomial ring over Q\mathbb QQ, and shapes and tableaux as finite-indexed Young diagrams. A generic ground-parameter value is asserted to exist as a theorem because the required unit and compatibility proofs are substantive.

The universal-ring milestone states all five parts of Theorem 3.19 for R‾0\overline R_0R0​ and R‾+\overline R_+R+​; part (5) is read inside FFF, where the universal uuu-admissible ring is the subring generated by q±1q^{\pm1}q±1, (q−1−q)−1(q^{-1}-q)^{-1}(q−1−q)−1, δ0−1\delta_0^{-1}δ0−1​ and ui±1u_i^{\pm1}ui±1​. The base-change statement uses S′⊗SWS'\otimes_S WS′⊗S​W for the source's W⊗SS′W\otimes_S S'W⊗S​S′. Theorem 4.8 is expressed as a product of full matrix algebras with tableau-sized blocks, combining its split and labeling clauses with the block dimensions stated elsewhere in §4. Theorem 6.1's Kauffman-tangle isomorphism is not posed because a corresponding tangle algebra has not been provided here. The cited spanning set is expressed as an indexed family, which remains meaningful when a degenerate coefficient ring identifies elements.

The goal requires an actual basis of cardinality rn(2n−1)!!r^n(2n-1)!!rn(2n−1)!! over an admissible integral domain. A mere dimension equality or spanning claim does not satisfy it. Contributions toward the missing generic decomposition, tableau count, base-change isomorphism, and passage to arbitrary admissible domains are all within scope. The ground-parameter and quotient-presentation definitions are reusable independently of this mission.

Selected references

  • F. M. Goodman and H. Hauschild Mosley, Cyclotomic Birman–Wenzl–Murakami algebras, II: Admissibility Relations and Freeness, 2008, arXiv:math/0612065v5.
16 thms3 active usersReviewed
Quantum Information·Captain: Goku

The operational meaning of quantum conditional informationResearch Paper

Motivation

How correlated are two quantum systems from the perspective of a third? We answer this by providing an optimal quantum state redistribution protocol for multipartite product sources. Specifically, given an arbitrary quantum state of three systems, where Alice holds two and Bob holds one, we identify the cost, in terms of quantum communication and entanglement, for Alice to give one of her parts to Bob. The communication cost gives the first known operational interpretation to quantum conditional mutual information. The optimal procedure is self-dual under time reversal and is perfectly composable. This generalizes known protocols such as the state merging and fully quantum Slepian-Wolf protocols, from which almost every known protocol in quantum Shannon theory can be derived.

This mission is the statement-level formalization of The operational meaning of quantum conditional information (arXiv:quant-ph/0612050v2). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

8 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Exact state-redistribution rate region and optimal corner (Main result: exact state-redistribution rate region and corner, Eqs. (1)–(2), PDF p. 2). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

2 results of the paper are not stated yet, because the library lacks an interface they need:

  • w-state: Independently moderated correction of the printed W-state numerical communication cost (source-ambiguity)
  • zero-communication-entanglement: Independently moderated correction of the printed flagged-state entanglement-cost sign (source-ambiguity)

Selected references

  • The operational meaning of quantum conditional information, arXiv:quant-ph/0612050v2, https://arxiv.org/abs/quant-ph/0612050v2
14 thms3 active usersReviewed
🏆Completed
Quantum Information·Captain: Goku

Algorithm to compute the rank and a Cartan subalgebra of a matrix Lie algebra with MathematicaResearch Paper

Motivation

We present in this paper a set of routines constructed to compute the rank of a matrix Lie algebra and also to determine a Cartan subalgebra from a given list of elements

This mission is the statement-level formalization of Algorithm to compute the rank and a Cartan subalgebra of a matrix Lie algebra with Mathematica (arXiv:math/0205235v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

16 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is so(n): BSo ordered basis (so(n): BSo ordered basis, PDF p. 5). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

2 results of the paper are not stated yet, because the library lacks an interface they need:

  • Abstract and introduction: rank/Cartan extension algorithm: A valid and fully specified exact Cartan-extension routine on the advertised real semisimple matrix embeddings, including guards and symbolic branch/parameter selection. (source-ambiguity)
  • Introduction, unnumbered Teorema: claimed Cartan characterization: A valid Cartan characterization with the original quantification over all real semisimple matrix embeddings and all their Cartan subalgebras. (source-ambiguity)

Selected references

  • Algorithm to compute the rank and a Cartan subalgebra of a matrix Lie algebra with Mathematica, arXiv:math/0205235v1, https://arxiv.org/abs/math/0205235v1
17 thms3 active usersReviewed
Quantum Information·Captain: Goku

Representation of Quantum Circuits with Clifford and π/8π/8π/8 GatesResearch Paper

Motivation

In this paper, we introduce the notion of a normal form of one qubit quantum circuits over the basis {H,P,T}\{H, P, T\}{H,P,T}, where HHH, PPP and TTT denote the Hadamard, Phase and π/8π/8π/8 gates, respectively. This basis is known as the {\it standard set} and its universality has been shown by Boykin et al. [FOCS '99]. Our normal form has several nice properties: (i) Every circuit over this basis can easily be transformed into a normal form, and (ii) Every two normal form circuits compute same unitary matrix if and only if both circuits are identical. We also show that the number of unitary operations that can be represented by a circuit over this basis that contains at most nnn TTT-gates is exactly 192⋅(3⋅2n−2)192 \cdot (3 \cdot 2^n - 2)192⋅(3⋅2n−2).

This mission is the statement-level formalization of Representation of Quantum Circuits with Clifford and π/8π/8π/8 Gates (arXiv:0806.3834v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

20 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Theorem 1 (seed paper result): unique exact normal form (Theorem 1 (seed paper result): unique exact normal form, PDF p. 6). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Selected references

  • Representation of Quantum Circuits with Clifford and π/8π/8π/8 Gates, arXiv:0806.3834v1, https://arxiv.org/abs/0806.3834v1
23 thms3 active usersReviewed
Quantum Information·Captain: Goku

Remarks on Matsumoto and Amano's normal form for single-qubit Clifford+T operatorsResearch Paper

Motivation

Matsumoto and Amano (2008) showed that every single-qubit Clifford+T operator can be uniquely written of a particular form, which we call the Matsumoto-Amano normal form. In this mostly expository paper, we give a detailed and streamlined presentation of Matsumoto and Amano's results, simplifying some proofs along the way. We also point out some corollaries to Matsumoto and Amano's work, including an intrinsic characterization of the Clifford+T subgroup of SO(3), which also yields an efficient T-optimal exact single-qubit synthesis algorithm. Interestingly, this also gives an alternative proof of Kliuchnikov, Maslov, and Mosca's exact synthesis result for the Clifford+T subgroup of U(2).

This mission is the statement-level formalization of Remarks on Matsumoto and Amano's normal form for single-qubit Clifford+T operators (arXiv:1312.6584v2). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

26 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is §1 main result: MA existence, uniqueness, optimality and effective normalization (§1 main result: MA existence, uniqueness, optimality and effective normalization, PDF p. 1). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Deferred results

4 results of the paper are not stated yet, because the library lacks an interface they need:

  • Theorem 5.1: matrix-input optimal exact synthesis: An operational exact-arithmetic synthesis machine over encoded quadratic/cyclotomic coefficients, implementing parity-driven U -> N^{-1}U recursion with a fixed Clifford lookup and charged arithmetic operations, while preserving absolute phase (or the specified Bloch image) and returning actual normal-form/elementary-word data. (hard)
  • Theorem 6.5: SO(3) ring characterization and synthesis: An operational exact-arithmetic synthesis machine over encoded quadratic/cyclotomic coefficients, implementing parity-driven U -> N^{-1}U recursion with a fixed Clifford lookup and charged arithmetic operations, while preserving absolute phase (or the specified Bloch image) and returning actual normal-form/elementary-word data. (hard)
  • Remark 6.6: linear SO(3) synthesis: An operational exact-arithmetic synthesis machine over encoded quadratic/cyclotomic coefficients, implementing parity-driven U -> N^{-1}U recursion with a fixed Clifford lookup and charged arithmetic operations, while preserving absolute phase (or the specified Bloch image) and returning actual normal-form/elementary-word data. (hard)
  • Section 8.1 Clifford E/X/S/omega coordinates: A correct coordinate range for the claimed unique E^a X^b S^c omega^d parametrization. (source-ambiguity)

Selected references

  • Remarks on Matsumoto and Amano's normal form for single-qubit Clifford+T operators, arXiv:1312.6584v2, https://arxiv.org/abs/1312.6584v2
31 thms3 active usersReviewed
Quantum Information·Captain: Goku

Remarks on the classical capacity of quantum channelResearch Paper

Motivation

A direct proof of the relation between the one-shot classical capacity and the minimal output entropy for covariant quantum channels is suggested. The structure of covariant channels is described in some detail. A simple proof of a general inequality for entanglement-assisted classical capacity is given.

This mission is the statement-level formalization of Remarks on the classical capacity of quantum channel (arXiv:quant-ph/0212025v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

7 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Irreducible covariance gives bistochasticity and the capacity–entropy identity (§1, theorem; (1)–(3), PDF p. 2). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Selected references

  • Remarks on the classical capacity of quantum channel, arXiv:quant-ph/0212025v1, https://arxiv.org/abs/quant-ph/0212025v1
16 thms3 active usersReviewed
🏆Completed
Quantum Information·Captain: Goku

Quantum data processing and error correctionResearch Paper

Motivation

This paper investigates properties of noisy quantum information channels. We define a new quantity called {\em coherent information} which measures the amount of quantum information conveyed in the noisy channel. This quantity can never be increased by quantum information processing, and it yields a simple necessary and sufficient condition for the existence of perfect quantum error correction.

This mission is the statement-level formalization of Quantum data processing and error correction (arXiv:quant-ph/9604022v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

8 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Coherent information bound and environment factorization criterion (§4, Eq.(4) and equality criterion, PDF p. 10). The milestones are the other numbered results, in the paper's order, each quoting the paper.

The paper's own objects are the definition item of this mission. Objects shared across papers come from the prove2quantum library and from earlier papers' missions, listed as references.

Provenance: prove2quantum's pipeline drafted each statement (gpt-6.1-sol on Stanford's Sherlock cluster). A blind read-back, written without seeing the paper, is attached to every item. An independent moderator compared each statement against the paper and passed the whole paper without edits.

Selected references

  • Quantum data processing and error correction, arXiv:quant-ph/9604022v1, https://arxiv.org/abs/quant-ph/9604022v1
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Computational Complexity·Captain: Lucas

PRIMES is in P: the polynomial Fermat congruence, the introspective groups, and the correctness of the Agrawal-Kayal-Saxena algorithmResearch Paper

PRIMES is in P: the polynomial Fermat congruence, the introspective groups, and the correctness of the Agrawal-Kayal-Saxena algorithm

1. Motivation

Agrawal, Kayal, and Saxena's "PRIMES is in P" (Annals of Mathematics 160 (2004) 781-793) settled a question open since the birth of complexity theory: primality has an unconditional, deterministic, polynomial-time test. The paper's algorithm is elementary - six steps: reject perfect powers; fix a small r; reject trivial factor witnesses; accept small inputs; test the congruence (X + a)^n = X^n + a modulo X^r - 1 for a = 1, ..., ell; accept. The mathematical heart is Lemma 2.1, a generalization of Fermat's Little Theorem to polynomial rings: for n at least 2 and a coprime to n, n is prime if and only if (X + a)^n = X^n + a in Z_n[X]. The correctness of the harder direction runs through the introspective machinery of Section 4: for a prime factor p of n with o_r(p) > 1, the numbers of I = {(n/p)^i p^j} are introspective for the polynomials of P = {the products of the generators X, X+1, ..., X+ell}; the residues of I generate a group G modulo r of size t > log^2 n; the images of P generate a group G-cal in the field F = F_p[X]/(h), h an irreducible factor of the r-th cyclotomic polynomial over F_p; Lenstra's lower bound and the Kalai-Sahai-Sudan upper bound on the size of G-cal collide unless n is a power of p, and step 1 excludes prime powers, so n is prime. Section 5 bounds the arithmetic work: O~(log^(21/2) n), unconditionally.

The mission formalizes the paper's mathematical content in Lean 4. The goal statement is Theorem 4.1: the algorithm of the algorithm layer returns PRIME if and only if n is prime. The milestones are the ingredients in attack order: the polynomial Fermat characterization (Lemma 2.1); the lcm lower bound (Lemma 3.1); the existence of a small r with large order (Lemma 4.3); the closure of introspection under multiplication (Lemmas 4.5 and 4.6); Lenstra's injectivity bound (Lemma 4.7); the Kalai-Sahai-Sudan collision bound (Lemma 4.8); and the polynomial work bound of Section 5 (Theorem 5.1, in generous integer form).

The source document is the uploaded paper (annals-v160-n2-p12.pdf in the mission materials).

2. The formalization fragment and conventions

The formalization is a two-layer development in the namespace AKS. The polynomial layer (AKS_poly) carries the congruences: congruence (1) as an equality in Z_n[X], congruence (2) as divisibility by X^r - 1 in Z_n[X], Definition 4.4's introspection relation over F_p[X], and the set P of products of the generators. The algorithm layer (AKS_alg) carries the arithmetic scaffolding and the algorithm itself: the integer logarithm, the multiplicative order, the lcm of the first numbers, the perfect-power predicate, the search for r, the loop bound, the six-step decision function, the set I and the residue group G, and the work measure of Section 5.

The following choices are disclosed explicitly.

  1. Compile verification by CI substitution. The authoring environment has no local Lean toolchain, so the compile check demanded by the mission is performed by the continuous integration of the repository (Lean 4.33 with Mathlib): all Lean code below was compiled there before this proposal was submitted, and the code attached to the items is byte-identical to the compiled modules.

  2. The theorem drafts carry sorry. The eight theorem statements are submitted as drafts for human review; each proof body is a single sorry marking the work the mission proposes to complete. The compilation therefore succeeds with exactly one "declaration uses 'sorry'" warning per theorem file.

  3. Generous integer encodings of the logarithms. The paper's real-valued log n appears in the algorithm only through the threshold o_r(n) > log^2 n of step 2 and the loop bound ell = floor(sqrt(phi(r)) log n) of step 5. The mission encodes both with logUp n = floor(log2 n) + 1, which is strictly larger than log2 n: step 2 searches for the smallest r with ordR r n > logUp(n)^2, and ell is the floor of the product of the square root of phi(r) and logUp n, encoded exactly as the floor of the square root of phi(r) logUp(n)^2. Both encodings are generous in the directions that preserve correctness: primes pass congruence (2) for every a and r, so a larger threshold and a longer loop never reject a prime; and for the converse the larger threshold and loop only strengthen the group bounds that force composites out. The integer bookkeeping of the final chain - floor(sqrt t) logUp n + 1 at least sqrt t log2 n - is part of the proposed work of the goal, with the generosity supplying the slack.

  4. The algorithm layer transcribes the six steps literally, with computable searches inside provable windows and classical decision where only the extension matters. ordR r a is the least k < r with a^k = 1 (mod r) - the window k < r is faithful because every multiplicative order divides phi(r) < r - and 0 when gcd(a, r) > 1. smallestR n searches the window bounded by the r_exists milestone's bound. aksDecide is stated with classical decision (open Classical, noncomputable): no execution of the test is ever needed, only its extensional behavior. aksWork is a computable schoolbook work measure charging logUp(n)^6 for step 1, r(logUp n + 1) for the searches of steps 2 and 3, and ell r n (logUp n + 1)(r + 1)^2 for the congruence loop of step 5.

  5. The groups are encoded by witness windows, and the two bounds are stated in the paper's forms. G is the Finset of residues modulo r of the numbers of I, encoded by the witness window i, j < r - faithful under the coprimality of n/p and p to r, because both orders then divide phi(r) at most r, so every residue of an I-number is achieved inside the window. Lemma 4.7 is stated in the paper's form: two distinct polynomials of P, both of degree less than t, map to distinct elements of F = F_p[X]/(h) (the field is AdjoinRoot h; the hypotheses carry h dividing X^r - 1, the primitivity - h not dividing X^k - 1 for 0 < k < r - irreducibility by instance, the introspectivity of I for P, and t at most the size of G). Lemma 4.8 is stated in the collision form: unless n is a power of p, there are m2 < m1 at most n^(floor(sqrt t)), colliding modulo r inside the bounded set I-hat, such that every image of P in F satisfies y^m1 = y^m2. The cardinality bookkeeping between these forms and the size of G-cal - stars-and-bars for the lower bound with the unique factorization of the generator products, and the root bound of a polynomial over a field for the upper - is carried by Mathlib and is part of the goal's proposed work.

  6. The field F = F_p[X]/(h) is taken with its factor h as an explicit parameter. The statements do not construct h; they carry h dividing X^r - 1, primitivity, and irreducibility as hypotheses (the latter two as Fact-class instances). The existence of h - an irreducible factor of the r-th cyclotomic polynomial over F_p of degree o_r(p), the standard fact of Lidl and Niederreiter cited as [LN] - is part of the mission's proposed work toward the goal.

  7. The "is in P" claim is anchored by an explicit work measure, with the bit-cost correspondence in prose. Milestone 7 bounds aksWork by C logUp(n)^15, a generous integer form of Theorem 5.1's O~(log^(21/2) n) - the generous exponent absorbs the schoolbook charging model and the logUp slack. The correspondence between arithmetic-work measures and Turing-machine bit complexity - the standard O~(m) arithmetic on m-bit numbers of the paper's Section 5 - is carried in prose; a machine-level formalization is out of scope.

  8. Pruned content. The paper's Section 5 refinements (Fouvry's Lemma 5.2 and the O~(log^(15/2) n) of Theorem 5.3, and the Lenstra-Pomerance variant), the conjectures (Artin's, the Sophie Germain density, Conjecture 6.1), and the historical survey of Section 1 are out of scope; the mission carries the unconditional Section 5 analysis only, in generous integer form, and the correctness theorem (Theorem 4.1) as the goal.

  9. Due diligence. Before creating the proposal, the creation script searches the platform for prior definitions and theorems matching the paper's ingredients; the search results are recorded in the repository's results directory for the reviewer.

  10. Definition names and module stems. The two definition bundles are published under names equal to their module stems (AKS_poly, AKS_alg), so that the platform imports Definitions.Def_AKS_* in the theorem preambles resolve, in dependency order poly, then alg (which imports poly).

3. Formalization targets

The mission has ten items: two reference definitions and eight theorem drafts, in the following order.

Reference definitions (the formalization fragment):

  • AKS_poly: the polynomial layer. Congruence (1) as the equality (X + a)^n = X^n + a in Z_n[X]; congruence (2) as divisibility by X^r - 1 in Z_n[X]; Definition 4.4's introspection relation over F_p[X]; and the set P of products of the generators X, X+1, ..., X+ell.
  • AKS_alg: the algorithm layer. The integer logarithm logUp; the multiplicative order ordR; the lcm of the first numbers; the perfect-power predicate; the six-step decision function aksDecide with its search smallestR and loop bound ell; the set I and the residue group G; and the work measure aksWork.

Theorem drafts (milestones in attack order, then the goal):

  1. AKS.poly_fermat: Lemma 2.1 - for n at least 2 and a coprime to n, n is prime if and only if (X + a)^n = X^n + a in Z_n[X] (Section 2).
  2. AKS.lcm_lower: Lemma 3.1 - the lcm of the first m numbers is at least 2^m for m at least 7 (Section 3).
  3. AKS.r_exists: Lemma 4.3 - for n > 1 there is an r with 1 < r at most max 3 (logUp n)^5 and ordR r n > logUp(n)^2 (Section 4).
  4. AKS.introspective_closure: Lemmas 4.5-4.6 - introspective numbers are closed under products, and introspectivity is closed under products of polynomials (Section 4).
  5. AKS.group_inj: Lemma 4.7 (Hendrik Lenstra Jr.) - two distinct polynomials of P, both of degree less than t, map to distinct elements of F = F_p[X]/(h), under the primitivity and introspectivity hypotheses, with t at most the size of the residue group G (Section 4).
  6. AKS.group_upper: Lemma 4.8 (Kalai-Sahai-Sudan) - unless n is a power of p, there are m2 < m1 at most n^(floor(sqrt t)), colliding modulo r inside the bounded set I-hat, such that every image of P in F satisfies y^m1 = y^m2 (Section 4).
  7. AKS.poly_time: the work bound - there is a constant C with aksWork n at most C logUp(n)^15 for every n, the generous integer form of Theorem 5.1 (Section 5).
  8. AKS.prime_iff (the goal): Theorem 4.1 - aksDecide n = PRIME if and only if n is prime (Section 4).

Milestones 1 to 7 correspond to the theorem drafts 1 to 7; the goal is draft 8.

4. Significance

The paper is one of the landmark results of computational number theory: a problem open since the 1960s - an unconditional, deterministic, polynomial-time primality test - solved by elementary means, in a proof whose only ingredients are the binomial theorem, Euler's function, and the root bound of a polynomial over a field. The formal account forces exactly what the prose leaves to convention: the precise ring in which each congruence lives, the precise windows in which the searches find their witnesses, the precise generosity of each integer rounding, and the precise content of the two group bounds. The paper's difficulty lies not in any single deep theorem but in the assembly of many small lemmas under one bound chain; a formalization makes each link explicit and checkable, and the mission's readback discipline gives an independent restatement check of every statement before review.

5. Difficulty

Milestone 1 is a commutation: the forward direction is the freshman's dream in Z_p[X] plus Fermat's little theorem for the base; the backward direction isolates the coefficient of X^q for a prime q with q^k dividing n exactly and computes its q-adic valuation below k. Milestone 2 is Nair's argument: the product of the primes in (m/2, m] divides the lcm. Milestone 3 is the counting argument: every bad r divides a single product below the lcm of the window, so some r in the window escapes. Milestone 4 is two ring commutations: f^(m m') = f(X^(m m')) along f(X^m)^(m') = f(X^(m m')), and the product rule for introspectivity. Milestone 5 is Lenstra's argument: from a collision in F and introspection, f(Y) - g(Y) acquires the t distinct primitive r-th roots indexed by G, exceeding its degree. Milestone 6 is the pigeonhole of I-hat against G, the non-power distinctness, and the collision equation transported by introspection. Milestone 7 is arithmetic over the windows. The goal assembles: Lemma 4.2's direction is the congruences for primes; the step-4 case is the factor below the square root; and the step-6 case is the chain of Lemma 4.9 - the injectivity lower bound, the collision upper bound, and the integer bookkeeping that the generous encodings close with slack.

6. Scope

Included: the two congruences and the introspection relation; the set P and the set I with the residue group G; the six-step algorithm; and the eight statements - the Fermat characterization, the lcm bound, the small-r existence, the two closure lemmas, the two group bounds, the work bound, and the correctness theorem.

Excluded, as disclosed in items 7 and 8 of section 2: the machine-level bit-cost formalization of "is in P" (carried in prose, anchored by the explicit aksWork measure); the Section 5 refinements (Fouvry's Lemma 5.2, the O~(log^(15/2) n) of Theorem 5.3, the Lenstra-Pomerance variant of [LP1]); the conjectures of Section 5 and Conjecture 6.1; and the historical survey of Section 1.

7. References

  • Manindra Agrawal, Neeraj Kayal, and Nitin Saxena, "PRIMES is in P", Annals of Mathematics 160 (2004) 781-793. The source document is the uploaded paper (annals-v160-n2-p12.pdf).
  • M. Nair, "On Chebyshev-type inequalities for primes", American Mathematical Monthly 89 (1982) 126-129 (the reference for Lemma 3.1).
  • Rudolf Lidl and Harald Niederreiter, Introduction to Finite Fields and their Applications, Cambridge University Press, 1986 (the reference [LN] for the factorization of the cyclotomic polynomial over F_p).
  • Hendrik W. Lenstra Jr., "Primality testing with cyclotomic rings", unpublished, August 2002 (the source of Lemma 4.7).
  • Adam Kalai, Amit Sahai, and Madhu Sudan, private communication, August 2002 (the source of the proof of Lemma 4.8).
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Metrology·Captain: Lucas

The CODATA 2022 adjustment: least squares, covariance propagation, and the self-consistency of the recommended valuesResearch Paper

Mission: The CODATA 2022 adjustment — least squares, covariance propagation, and the self-consistency of the recommended values

Motivation

Every value of a fundamental constant used in science — the fine-structure constant, the Newtonian constant of gravitation, the Rydberg constant — comes from one place: the least-squares adjustment periodically carried out by the CODATA Task Group on Fundamental Constants. The 2022 adjustment (P. J. Mohr, D. B. Newell, B. N. Taylor and E. Tiesinga, CODATA recommended values of the fundamental physical constants: 2022) takes 133 input data, determines 79 adjusted constants by weighted least squares with 54 degrees of freedom, applies expansion factors 1.7 and 2.5 to the uncertainties of certain groups of data to reduce all normalized residuals to two or less, obtains a final chi-square of 44.2 with Birge ratio 0.90, treats the sixteen values of the Newtonian constant of gravitation separately (16 data, one adjusted constant, 15 degrees of freedom, chi-square 12.9, expansion factor 3.9, Birge ratio 0.93), and obtains the recommended values from the adjusted constants by propagating their uncertainties and covariances.

The mission formalizes the mathematical skeleton of this process in Lean 4 and audits a representative slice of its output by exact rational arithmetic: the equivalence between minimizers of the chi-square statistic and solutions of the normal equations, the weighted mean as the rank-one case (the situation of the separate adjustment of G), the printed degrees of freedom and Birge ratios, the effect of uncertainty expansion on covariances and correlations, the algebraic laws of relative-uncertainty propagation, the exact derived constants determined by the exact defining values of h, e, k and N_A, and the mutual consistency of the printed uncertainties of the alpha family. The goal theorem packages these into the statement that the 2022 adjustment is self-consistent.

What is being formalized is the statistics and the arithmetic of the adjustment, not any physical measurement: the input data enter only through the abstract structure of a weighted least-squares problem, and the numerical audits compare exact rationals with the digit strings printed in the report's tables.

The fragment and its conventions

The source is the 2022 CODATA report in its two identical published versions: J. Phys. Chem. Ref. Data 54, 033105 (2025), doi 10.1063/5.0279860, and Rev. Mod. Phys. 97, 025002 (2025), doi 10.1103/RevModPhys.97.025002. The mission formalizes section XII, "Least-squares adjustment", and the exact and recommended values of Tables XXXII and XXXIII, under the following disclosed conventions.

Twelve conventions deserve disclosure. First, the platform publishes definitions as modules, so the three definition bundles — the least-squares model, the correlations and uncertainty propagation, and the exact rational values — are published as platform definitions (CODATA_lsa, then CODATA_uncert which imports it, and CODATA_values), attached to the proposal as reference items; the theorem drafts import them; and the creation script reads the definition code and the theorem statements directly from the repository modules that the CI has just compiled, so the code posted to the platform is byte-identical to the code whose compilation the CI verified. Second, the two uploaded PDFs are the same paper in its two published versions; citations reference both, and the table numbering follows the Rev. Mod. Phys. version (Tables XXXII-XXXIII, section XII). Third, the observational equations are taken in linear form; the report's observational equations are linear in the adjusted constants to begin with, but the values of the input data, the design matrix entries and the offset vector are interface data, not formalized: the theorems quantify over all weighted least-squares problems of the recorded dimensions. Fourth, the chi-square distribution and the printed probability values (83 percent for the main adjustment, 61 percent for G) are statistical statements about the chi-square distribution; they are printed data of the report and are not constructed, and no probability theory enters the mission. Fifth, the Newtonian constant of gravitation is treated separately, exactly as in the report: a second least-squares structure with sixteen input data and one adjusted constant, its own expansion factor 3.9, and its own Birge ratio; the goal theorem relates the two adjustments only through their common formalism. Sixth, the expansion factors 1.7 and 2.5 of the main adjustment are recorded in the description but not formalized, because the data they modify are interface data; the expansion factor 3.9 of the G adjustment is formalized through the covariance expansion law applied to the abstract covariance matrix of the sixteen values. Seventh, matrix inversion is expressed by two-sided inverse predicates, written entry by entry against the Kronecker delta, rather than through an inverse operator; this keeps the statements elementary and avoids any dependence on matrix inverse lemmas. Eighth, all arithmetic is rational or real: the exact constants are rationals, the derived quantities K_J, R_K, Phi_0, G_0, G_0⁻¹, F, R and the electronvolt are exact rationals, and the printed digit strings are captured by rational rounding intervals; exact quantities carrying a factor of pi (hbar, the Stefan-Boltzmann constant) and quantities with experimental uncertainty outside the audited family (the dalton, the Newtonian constant itself) are excluded because they are not rational. Ninth, the Birge ratios are captured by the rounding intervals [0.895, 0.905) and [0.925, 0.935), which the printed two-digit values 0.90 and 0.93 determine; the true values are sqrt(44.2/54) and sqrt(12.9/15). Tenth, the alpha family audit is an existential: the printed two-significant-digit uncertainties of alpha, 1/alpha, mu_0, eps_0 and Z_0 are jointly reproduced by a single rational relative-uncertainty witness of order 1.6 × 10⁻¹⁰, supplied explicitly by the prover (for example 156/10¹²); this witnesses consistency without asserting the (irrational, distribution-laden) exact relative uncertainty of alpha. Eleventh, the read-backs attached to the theorem drafts were authored by the same model that produced the statements (readback_model glm-5-latest-short); they are a self-check, not an independent audit, and human review of every item is required before submission. Twelfth, everything is developed against the platform's Mathlib build (0df444a); the compilation check of every item is the repository CI, which builds all definitions and theorem drafts with the same Mathlib version (no local Lean toolchain is available to the drafting agent, and this is disclosed).

Formalization targets

Eleven items: three published definition bundles attached as references, seven milestone theorem drafts, and the goal theorem.

  • The least-squares model of the adjustment (reference): the LSQ structure with data, uncertainties, correlations, design matrix, offsets and the weight matrix as a two-sided inverse of the covariance matrix; residuals, the chi-square statistic, the normal equations, the minimization property, the normal matrix and its two-sided inverses, strict positive definiteness, the covariance matrix, the degrees of freedom N - M, and the Birge ratio sqrt(chi²/nu) (section XII).
  • Correlations and uncertainty propagation (reference): the correlation coefficient of a covariance matrix, the expansion of a covariance matrix by per-entry factors, and the relative-variance functional of the propagation law (section XII).
  • The exact rational values (reference): c, h, e, k and N_A exactly as fixed by the SI revision, the derived exact quantities 2e/h, h/e², h/2e, 2e²/h, h/2e², N_A e, N_A k, the electronvolt and h/e, and the 2022 rational values of alpha, 1/alpha, mu_0, eps_0 and Z_0 (Tables XXXII-XXXIII).
  • The normal equations characterize the minimizers, and the solution is unique at full column rank — milestone.
  • The single adjusted constant is the weighted mean with variance the inverse of the total weight, uniquely determined — milestone.
  • The printed degrees of freedom and Birge ratios: 133 - 79 = 54, 16 - 1 = 15, and the rounding intervals of sqrt(44.2/54) and sqrt(12.9/15) — milestone.
  • Expansion of uncertainties: a common factor squares the covariances and preserves every correlation; equal factors on the two members of a pair suffice — with the expansion factor 3.9 of the G adjustment as the instance — milestone.
  • The laws of propagation of relative uncertainty: unit self-correlations, single-component variances, quadratic scaling, and addition of variances for uncorrelated inputs — milestone.
  • The exact derived constants agree with the printed digit strings of Table XXXIII: K_J, R_K, Phi_0, G_0, G_0⁻¹, F, R, the electronvolt and h in eV Hz⁻¹ — milestone.
  • A single rational relative-uncertainty witness reproduces the printed uncertainties of the whole alpha family — milestone.
  • The 2022 adjustment is self-consistent: the goal, packaging the degrees of freedom, the two minimizations, the two Birge ratios, the correlation preservation under the expansion factor 3.9, the alpha-family witness, and the derived-value audit — the goal.

Significance

The CODATA adjustment is the mechanism by which the values of the fundamental constants become internationally accepted, self-consistent numbers; every precision measurement and every physical theory that quotes a constant inherits from it. The mission makes the three layers of the mechanism checkable by a proof assistant: the statistics (the least-squares theorem that the adjustment procedure is, by construction, the unique minimum of the chi-square statistic), the data hygiene (the effect of uncertainty expansion on covariances and correlations, and the propagation laws by which the recommended values and their uncertainties are derived), and the arithmetic (an exact rational audit confirming that the printed digit strings of the derived constants and the printed Birge statistics are consistent with the exact defining values and the reported chi-squares). Because the 2019 SI revision fixed h, e, k and N_A exactly, a growing family of derived constants is a pure rational computation; the mission verifies a representative slice of that family to the printed precision.

Difficulty

The milestones are honest and of mixed difficulty. The normal-equations milestone is the mathematical heart: the chi-square statistic is a quadratic form in the adjusted constants, strict positive definiteness of the weight matrix makes it convex, and the equivalence with the normal equations plus uniqueness at full column rank is a complete weighted least-squares existence-uniqueness argument, carried out entry by entry without matrix inverse lemmas. The weighted-mean milestone is a direct computation in the rank-one case, complicated only by the bookkeeping of the two-sided inverse predicate for the one-by-one normal matrix. The Birge milestone is real arithmetic: two subtractions and two square-root bounds, each reducible to exact rational comparisons by squaring. The expansion and propagation milestones are algebra over the reals: square roots of products of positive reals and the cancellation of equal factors; their difficulty is bookkeeping, not ideas. The derived-values and alpha-family milestones are exact rational computations with numerators and denominators up to thirty digits; they are fully decidable, and their difficulty is the size of the arithmetic — the prover must exhibit the witness ur and verify fifteen rational interval inclusions — for which norm_num-style automation is intended. The goal assembles the parts. Nothing in the mission requires mathematics beyond convexity of a quadratic form and exact rational arithmetic, and this is the point: the CODATA adjustment, the most authoritative computation in metrology, is at its core an auditable exact computation.

Formalization scope

Every theorem quantifies only over abstract least-squares structures and rational values; no measurement, no physical theory, and no probability distribution enters. The fragment excludes: the 133 input data as concrete vectors and the 79 adjusted constants as concrete quantities; the chi-square distribution and all probability statements; the least-squares fitting of the theoretical expressions (atomic transition frequencies, muonic Lamb shifts, magnetic-moment anomalies); the 2022-versus-2018 value comparisons and the historical narrative; the mises en pratique and the experimental methods; the electroweak and particle-physics input data; the quantities whose exact values involve pi (hbar, the Stefan-Boltzmann constant) or whose values carry experimental uncertainty outside the audited family; and the correlations among the input data as concrete numbers. What is formalized is the statistical skeleton, the covariance algebra, and the exact rational audit of the printed output.

Selected references

  • P. J. Mohr, D. B. Newell, B. N. Taylor and E. Tiesinga, CODATA recommended values of the fundamental physical constants: 2022, J. Phys. Chem. Ref. Data 54, 033105 (2025), doi 10.1063/5.0279860; Rev. Mod. Phys. 97, 025002 (2025), doi 10.1103/RevModPhys.97.025002 — the mission's source (uploaded by the proposer in both versions): section XII and Tables XXXII-XXXIII.
  • Resolution 1 of the 26th CGPM (2018) — the exact defining values of h, e, k and N_A on which the derived-value audit rests.
  • B. N. Taylor and C. E. Kuyatt, Guidelines for evaluating and expressing the uncertainty of NIST measurement results (1994), and the Guide to the Expression of Uncertainty in Measurement (JCGM 100) — the law of propagation of uncertainty that the propagation milestones formalize.
  • R. T. Birge (1932) and the subsequent least-squares tradition of the constants — the Birge ratio R_B = sqrt(chi²/nu) and the normalized-residual criterion that the expansion factors implement.
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Operations ResearchOptimizationQuantum Information·Captain: mikedeng1

An Optimal Product-State Approximation for 2-Local Quantum Hamiltonians with Positive Terms: Rounding Level 2 of the Quantum Lasserre Hierarchy Gives a 1/2-Approximation for Quantum Max CutResearch Paper

Motivation

Quantum Max Cut assigns a qubit to each vertex of a weighted graph and a two-qubit energy term to each edge. It asks for a quantum state with high total energy. The problem is a quantum analogue of graph Max Cut, but states can be entangled and edge terms act on a Hilbert space whose dimension grows exponentially with the number of vertices. Approximation algorithms therefore need a compact way to reason about the best quantum state without describing that state explicitly. Gharibian and Parekh's 2019 algorithm used product-state rounding for a quantum Max Cut relaxation; Parekh and Thompson's level-2 work showed why stronger quantum relaxations matter. The present paper combines a level-2 relaxation with a different treatment of highly valued edges to obtain a one-half guarantee.

The target is a known result from the pinned version arXiv:2206.08342v2, not an open conjecture. This mission isolates its Quantum Max Cut theorem. The paper also treats other positive 2-local Hamiltonians and a separate guarantee for graphs of prescribed minimum degree; neither is part of this target.

Setting

Let G=(V,E)G=(V,E)G=(V,E) be a finite undirected graph with a nonnegative weight wijw_{ij}wij​ on each edge, and put one qubit at each vertex. Write Xi,Yi,ZiX_i,Y_i,Z_iXi​,Yi​,Zi​ for the three Pauli operators acting on qubit iii. The edge Hamiltonian and total Quantum Max Cut Hamiltonian are

Hij=I−XiXj−YiYj−ZiZj4,H=∑{i,j}∈EwijHij.H_{ij}=\frac{I-X_iX_j-Y_iY_j-Z_iZ_j}{4},\qquad H=\sum_{\{i,j\}\in E}w_{ij}H_{ij}.Hij​=4I−Xi​Xj​−Yi​Yj​−Zi​Zj​​,H={i,j}∈E∑​wij​Hij​.

Every undirected edge appears once. A density matrix σ\sigmaσ is positive semidefinite with trace one. Its energy is Tr⁡(Hσ)\operatorname{Tr}(H\sigma)Tr(Hσ), and λmax⁡(H)\lambda_{\max}(H)λmax​(H) is the largest energy attainable by any density matrix, including an entangled one.

A Pauli polynomial is a real linear combination of tensor products of I,X,Y,ZI,X,Y,ZI,X,Y,Z. A monomial's degree counts its nonidentity factors. A kkk-positive pseudo-density ρ~\widetilde\rhoρ​ is Hermitian, has trace one, and satisfies Tr⁡(ρ~P2)≥0\operatorname{Tr}(\widetilde\rho P^2)\ge0Tr(ρ​P2)≥0 for every Pauli polynomial PPP of degree at most kkk. The level-2 quantum Lasserre relaxation maximizes Tr⁡(Hρ~)\operatorname{Tr}(H\widetilde\rho)Tr(Hρ​) over all such pseudo-densities. It is an upper bound on the unrestricted quantum optimum, even though ρ~\widetilde\rhoρ​ itself need not be positive semidefinite. These definitions are from pp. 6–8 of the paper.

For an edge, its relaxed value is μij=Tr⁡(Hijρ~)\mu_{ij}=\operatorname{Tr}(H_{ij}\widetilde\rho)μij​=Tr(Hij​ρ​). The rescaled value vijv_{ij}vij​ is defined by μij=(1+3vij)/4\mu_{ij}=(1+3v_{ij})/4μij​=(1+3vij​)/4. Algorithm 4 chooses a threshold γ\gammaγ, puts every edge with vij>γv_{ij}>\gammavij​>γ in LLL, and calls vertices incident to no edge in LLL the set BBB. It assigns the two-qubit mixed state (I−ZiZj)/4(I-Z_iZ_j)/4(I−Zi​Zj​)/4 to each edge in LLL. Vertices in BBB receive single-qubit states obtained by normalizing three independent Gaussian projections of the relaxation's rounding vectors. The output ρ\rhoρ is the product of those factors, as in equation (5), p. 14. The large edges form a matching at the selected threshold, so those factors occupy disjoint qubits. The Gaussian draw is the algorithm's only randomness.

Formalization targets

Theorem 3: a one-half approximation

The goal is the paper's Theorem 3, p. 17. A single threshold must work for every graph and every nonnegative edge weighting:

∃γ∈(−1/3,1]∀H of the form above,ETr⁡(HρAlg4)≥12λmax⁡(H).\exists\gamma\in(-1/3,1]\quad \forall H\text{ of the form above},\qquad \mathbb E\operatorname{Tr}(H\rho_{\mathrm{Alg4}}) \ge \frac12\lambda_{\max}(H).∃γ∈(−1/3,1]∀H of the form above,ETr(HρAlg4​)≥21​λmax​(H).

The level-2 solution used by Algorithm 4 is optimal for the given HHH. The goal also says that the matrix output is a density matrix for every Gaussian outcome. Its threshold is existential because the theorem does not fix a decimal constant; the paper subsequently selects 0.9110.9110.911 for its analysis.

Supporting results

The fourteen milestones follow the order in which the proof of Theorem 3 uses them.

  1. Relaxation and assembly. Lemma 9 (p. 28): the level-kkk value νk(H)\nu_k(H)νk​(H) is at least λmax⁡(H)\lambda_{\max}(H)λmax​(H). Proposition 1 (p. 9), for strictly quadratic 2-local Hamiltonians (Definition 3): if Tr⁡(Hijρ)≥αμij\operatorname{Tr}(H_{ij}\rho)\ge\alpha\mu_{ij}Tr(Hij​ρ)≥αμij​ on every edge, then Tr⁡(Hρ)≥αλmax⁡(H)\operatorname{Tr}(H\rho)\ge\alpha\lambda_{\max}(H)Tr(Hρ)≥αλmax​(H). Lemma 5 (p. 17): μij∈[0,1]\mu_{ij}\in[0,1]μij​∈[0,1], vij∈[−1/3,1]v_{ij}\in[-1/3,1]vij​∈[−1/3,1], sij∈[−1,1]s_{ij}\in[-1,1]sij​∈[−1,1] for k≥2k\ge2k≥2.
  2. Edges inside BBB. Lemma 4 (p. 12): for a k×dk\times dk×d standard Gaussian matrix ZZZ and unit u,vu,vu,v,
E[Zu∥Zu∥⋅Zv∥Zv∥]=F(k,u⋅v),F(k,t)=2k(Γ(k+12)Γ(k2))2t 2F1(12,12;k2+1;t2).\mathbb E\Big[\tfrac{Zu}{\|Zu\|}\cdot\tfrac{Zv}{\|Zv\|}\Big]=F(k,u\cdot v),\qquad F(k,t)=\frac2k\Big(\frac{\Gamma(\frac{k+1}2)}{\Gamma(\frac k2)}\Big)^2t\,{}_2F_1\big(\tfrac12,\tfrac12;\tfrac k2+1;t^2\big).E[∥Zu∥Zu​⋅∥Zv∥Zv​]=F(k,u⋅v),F(k,t)=k2​(Γ(2k​)Γ(2k+1​)​)2t2​F1​(21​,21​;2k​+1;t2).

Equation (7) (p. 17): Gaussian product-state rounding earns (1+F(3,vij))/4(1+F(3,v_{ij}))/4(1+F(3,vij​))/4 in expectation on edge ijijij. Lemma 6 (p. 18) reduces min⁡v∈(−1/3,γ](1+F(3,v))/(1+3v)≥1/2\min_{v\in(-1/3,\gamma]}(1+F(3,v))/(1+3v)\ge1/2minv∈(−1/3,γ]​(1+F(3,v))/(1+3v)≥1/2 to two checks at γ\gammaγ; Definition 13 (p. 19) asserts that γ=0.911\gamma=0.911γ=0.911 passes them; Fact 1 (p. 16) is the resulting factor 1/21/21/2 on edges with both ends in BBB. 3. Monogamy. The 4×44\times44×4 SWAP Gram matrix M(p,q,r)M(p,q,r)M(p,q,r) of three qubits is positive semidefinite (p. 20). Lemma 8 (p. 22): M⪰0M\succeq0M⪰0 and q≤0q\le0q≤0 imply p≥−3/2p\ge-\sqrt3/2p≥−3​/2. Fact 2 (p. 16): if vij>0.911v_{ij}>0.911vij​>0.911 then vik<1/3v_{ik}<1/3vik​<1/3. Remark 3 (p. 19): the large edges form a matching. 4. Edges touching LLL. Equation (12) (p. 19): (I−Z⊗Z)/4(I-Z\otimes Z)/4(I−Z⊗Z)/4 earns 1/2≥μij/21/2\ge\mu_{ij}/21/2≥μij​/2 on a large edge. The last display of the proof of Theorem 3 (p. 19): an edge adjacent to LLL earns exactly 1/4>μij/21/4>\mu_{ij}/21/4>μij​/2.

Significance

The theorem guarantees half of the optimum over all quantum states while returning a state built from one- and two-qubit product factors. This is stronger than a guarantee relative only to the best product state: the benchmark permits entanglement. It also explains why a level-2 relaxation has algorithmic value for this problem. The comparison and the claimed approximation factor are established in the paper; formalizing them would leave a reusable verified interface for finite-qubit Pauli polynomials, pseudo-densities, and Gaussian product-state rounding.

The formal work still needed is a machine-checked proof of the known theorem and its milestones. The published register, Pauli, density-matrix and standard-Gaussian-vector definitions can be reused. The source's separate results for other positive 2-local Hamiltonians would need additional models and theorems, beyond this mission.

Difficulty

Level-1 Gaussian product-state rounding alone does not reach one half uniformly: the paper identifies an edge range where its ratio falls below 0.50.50.5. Large edge values cannot be handled by the same rounding estimate. A level-2 pseudo-density supplies stronger constraints between adjacent edges, but it is not itself a physical state, so ordinary positivity of ρ~\widetilde\rhoρ​ is unavailable. The source's SWAP matrix and threshold analysis express the needed restrictions. The paper's printed dual certificate for Lemma 8 has a coordinate-order erratum; the lemma's statement remains the target.

Formalization scope

Qubits are indexed by Fin n (the paper uses 1,…,n1,\ldots,n1,…,n), with basis Fin n → Bool. Operators are complex matrices. The real part of a trace represents the expectation of a Hermitian expression. The maximum eigenvalue is stated through comparison with every density matrix; for Hermitian HHH, this is equivalent to comparing with its largest eigenvalue. Expected energy is a Bochner integral over a probability measure carrying independent standard Gaussian coordinates. A zero Gaussian projection is assigned Bloch vector zero, giving the maximally mixed one-qubit state at that outcome.

The rounding vectors are given with unit norms and exactly the Gram matrix obtained from the level-2 solution. The output state is computed as the matrix product in equation (5); energy is traced against that matrix. Positivity is required for every real degree-2 Pauli polynomial, and the pseudo-density is required to be optimal. These choices exclude vacuous variants based on degree-1 positivity, free Bloch vectors, or edge energies supplied as assumptions. The finite operator model also covers an empty graph; the approximation inequality there is 0≥00\ge00≥0.

The statement formalizes the approximation guarantee and state validity. The polynomial running-time clause of the paper's general approximation definition is outside this Lean statement. Reusable contributions include the Pauli-polynomial interface, matrix and moment identities for pseudo-densities, integrability and measurability facts for the Gaussian rounding, and the SWAP semidefinite bound.

Selected references

  • Ojas Parekh and Kevin Thompson, An Optimal Product-State Approximation for 2-Local Quantum Hamiltonians with Positive Terms, arXiv preprint, 2022, version 2 dated 2026. arXiv:2206.08342.
  • Sevag Gharibian and Ojas Parekh, Almost Optimal Classical Approximation Algorithms for a Quantum Generalization of Max-Cut, APPROX/RANDOM, 2019. DOI:10.4230/LIPIcs.APPROX-RANDOM.2019.31.
  • Ojas Parekh and Kevin Thompson, Application of the Level-2 Quantum Lasserre Hierarchy in Quantum Approximation Algorithms, ICALP, 2021. arXiv:2105.05698.
  • Jop Briët, Fernando Mário de Oliveira Filho and Frank Vallentin, Grothendieck Inequalities for Semidefinite Programs with Rank Constraint, Theory of Computing 10, 2014, 77–105. Journal article.
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Category TheoryFunctional AnalysisTopology·Captain: mikedeng1

Gelfand-type duality for commutative von Neumann algebras: The Opposite Category of Commutative von Neumann Algebras Is Equivalent to Measurable Locales, Hyperstonean Locales and Spaces, and CSLEMSResearch Paper

Motivation

Gelfand duality identifies compact Hausdorff spaces with commutative unital C*-algebras: a space XXX corresponds to the algebra C(X)C(X)C(X) of continuous complex functions, and continuous maps correspond contravariantly to unital *-homomorphisms (Gelfand 1941; in categorical form, Negrepontis 1971). Measure theory has an analogous expectation. A measurable space with a σ-ideal of negligible sets yields the commutative von Neumann algebra L∞L^\inftyL∞ of bounded measurable functions modulo equality almost everywhere, and every commutative von Neumann algebra should arise in this way. Making that expectation precise as an equivalence of categories requires deciding which measurable spaces to allow and which maps between them to identify.

Timeline. Stone (1936–1937) established the duality between Boolean algebras and Stone spaces, and between complete Boolean algebras and extremally disconnected ones. Segal (1951) introduced localizable measure spaces. Dixmier (1951) characterized the Gelfand spectra of commutative von Neumann algebras as the hyperstonean spaces. Loomis (1947) and Sikorski (1948) represented σ-complete Boolean algebras as measurable sets modulo meager sets on their Stone spaces. Von Neumann (1932), Maharam (1958), Ionescu Tulcea (1965), Vesterstrøm–Wils (1969), Edgar (1976) and Graf (1980) gave criteria for lifting homomorphisms of measure algebras to point maps. Pavlov (arXiv:2005.05284, J. Pure Appl. Algebra) assembled these ingredients into one equivalence of categories. That equivalence is the subject of this mission.

Setting

An enhanced measurable space (X,M,N)(X,M,N)(X,M,N) is a set XXX, a σ-algebra MMM of subsets of XXX, and a σ-ideal N⊆MN\subseteq MN⊆M of the power set 2X2^X2X, the negligible sets. A premap f ⁣:(X,M,N)→(X′,M′,N′)f\colon(X,M,N)\to(X',M',N')f:(X,M,N)→(X′,M′,N′) is a map defined on a conegligible subset of XXX with f∗M′⊆Mf^*M'\subseteq Mf∗M′⊆M and f∗N′⊆Nf^*N'\subseteq Nf∗N′⊆N. Two premaps are weakly equal almost everywhere, f≈gf\approx gf≈g, when f∗m⊕g∗m∈Nf^*m\oplus g^*m\in Nf∗m⊕g∗m∈N for every m∈M′m\in M'm∈M′. The space is compact if some compact class K⊆MK\subseteq MK⊆M (a family with the finite intersection property for all subfamilies) has a non-negligible member inside every non-negligible measurable set. It is strictly localizable if it is isomorphic, through premaps, to a coproduct of a small family of spaces carrying faithful finite measures. CSLEMS is the category of compact strictly localizable spaces with ≈\approx≈-classes of premaps.

A frame is a complete lattice in which finite meets distribute over arbitrary joins; the category of locales is the opposite of the category of frames. A complete Boolean algebra is localizable if 111 is the supremum of the elements aaa for which aAaAaA carries a finite faithful continuous valuation. MLoc, the category of measurable locales, is the full subcategory of locales on the localizable Boolean algebras. A hyperstonean locale is a Stonean locale (coherent, regular, ¬x∨¬¬x=1\neg x\vee\neg\neg x=1¬x∨¬¬x=1) in which every nonzero open has a positive normal valuation not vanishing on it. A hyperstonean space is a sober space whose locale of opens is hyperstonean. HStoneanLoc and HStonean take open maps as morphisms. CVNA is the category of commutative von Neumann algebras (C*-algebras with a predual) and normal unital *-homomorphisms.

Formalization targets

Goal: Theorem 1.1

HStonean≃HStoneanLoc,HStoneanLoc≃MLoc,CSLEMS≃MLoc,MLoc≃CVNAop.\mathsf{HStonean}\simeq\mathsf{HStoneanLoc},\qquad \mathsf{HStoneanLoc}\simeq\mathsf{MLoc},\qquad \mathsf{CSLEMS}\simeq\mathsf{MLoc},\qquad \mathsf{MLoc}\simeq\mathsf{CVNA}^{\mathrm{op}}.HStonean≃HStoneanLoc,HStoneanLoc≃MLoc,CSLEMS≃MLoc,MLoc≃CVNAop.

The goal is the existence of the four equivalences. It does not fix the functors.

The four equivalences with their functors

  • Proposition 2.72: the equivalence HStonean≃HStoneanLoc\mathsf{HStonean}\simeq\mathsf{HStoneanLoc}HStonean≃HStoneanLoc is implemented by the locale of opens Ω\OmegaΩ.
  • Proposition 2.73: the equivalence HStoneanLoc≃MLoc\mathsf{HStoneanLoc}\simeq\mathsf{MLoc}HStoneanLoc≃MLoc is implemented by the compact opens COpen\mathrm{COpen}COpen.
  • Theorem 3.20: the equivalence MLoc≃CVNAop\mathsf{MLoc}\simeq\mathsf{CVNA}^{\mathrm{op}}MLoc≃CVNAop has inverse ProjLoc\mathsf{ProjLoc}ProjLoc, given by projections and restriction.
  • Theorem 5.19: the equivalence CSLEMS≃MLoc\mathsf{CSLEMS}\simeq\mathsf{MLoc}CSLEMS≃MLoc is implemented by ML\mathsf{ML}ML, the functor (X,M,N)↦M/N(X,M,N)\mapsto M/N(X,M,N)↦M/N, f↦f∗f\mapsto f^*f↦f∗.

Supporting milestones

The supporting milestones, in proof order:

  • normal valuations versus continuous valuations on compact opens (Lemma 2.58);
  • localizability through valuations (Lemma 2.53);
  • completeness of ProjAlg(A)\mathsf{ProjAlg}(A)ProjAlg(A) (Proposition 3.8);
  • A∗A_*A∗​ as continuous valuations (Proposition 3.9);
  • ProjAlg\mathsf{ProjAlg}ProjAlg as a functor (Lemma 3.11);
  • σ-complete algebras with faithful valuations (Lemma 4.55);
  • strict localizability implies localizability (Proposition 4.54);
  • compactness of induced subspaces (Lemma 4.61);
  • measurable images (Proposition 4.65);
  • TM\mathrm{TM}TM on hyperstonean spaces (Proposition 5.4);
  • ML\mathsf{ML}ML on morphisms (Lemma 5.11);
  • the isomorphism (X,M,N)≅Spec(ML(X,M,N))(X,M,N)\cong\mathrm{Spec}(\mathsf{ML}(X,M,N))(X,M,N)≅Spec(ML(X,M,N)) (Proposition 5.16).

Significance

The result. Theorem 1.1 replaces commutative von Neumann algebras, a class of operator algebras, by measurable locales, which are pointless spaces. It also gives a point-set model, CSLEMS, in which morphisms are measurable maps modulo a null relation. With it, constructions on commutative von Neumann algebras can be carried out measure-theoretically and transported back: products, pushforwards of measures, and the identification of the predual with valuations. It also explains why the obvious choices fail. With localizable instead of strictly localizable spaces, with equality almost everywhere instead of weak equality, or without compactness, the measure-theoretic category is not dual to CVNA (Remarks 4.23 and 5.18).

Formalization. The theorem is proved in the paper. None of the five categories, and none of the equivalences, has a machine-checked form in Mathlib or on the platform. Mathlib has W*-algebras (WStarAlgebra), locales, Stonean spaces and Baire-measurable sets, but no normal homomorphisms, measure algebras or lifting theorems. The published module QAlgorithms_Papers_Independent_Support21_P20 formalizes this paper's valuations, enhanced measurable spaces and premaps, and poses several lemmas, three of which are milestones here. Completing the mission means formalizing Stone and Stonean duality for locales, the spectral theory of commutative von Neumann algebras through projections, and the von Neumann–Maharam lifting theorem for strictly localizable spaces.

Difficulty

The equivalences in §2 restrict classical dualities and are mostly bookkeeping once those dualities are available. Even so, Mathlib's Stone duality is not stated for locales with open maps. The central difficulty is Proposition 5.16. An object of CSLEMS must be isomorphic, through point maps, to the Stone spectrum of its own measure algebra. In one direction this needs a lifting M/N→MM/N\to MM/N→M that is a Boolean homomorphism, and that uses strict localizability through the von Neumann–Maharam theorem. In the other direction it needs a point map from the spectrum back to XXX, constructed from the compact class. The natural first idea, choosing representatives class by class, does not give a homomorphism: liftings exist only through a transfinite construction. A second difficulty is Lemma 5.11. A Boolean homomorphism induced by a measurable map preserves countable suprema, but in general it does not preserve arbitrary ones (Remark 5.12). Compactness and the measurable image of Proposition 4.65 are what rule this out.

Formalization scope

All five categories live in one universe, with objects in Type u. The encoding commits to these conventions:

  • CSLEMS. Morphisms are partial premaps (X → Option Y) modulo weak equality almost everywhere. Theorem 1.1's bullet speaks of maps of sets, but with total maps the theorem is false: (pt,2pt,2pt)(\mathrm{pt},2^{\mathrm{pt}},2^{\mathrm{pt}})(pt,2pt,2pt) has no map to ∅\varnothing∅ (Remarks 4.9, 4.15). Strict localizability uses a small index family and isomorphism in PreEMS; the faithful finite measures of its σ-finite pieces are countably additive maps M→CM\to\mathbb CM→C with absolutely convergent sums (Remark 4.29), because Definition 4.28's saturation clause alone would also admit merely finitely additive ones. Compactness quantifies over arbitrary subfamilies, not countable ones.
  • MLoc. The full subcategory of Mathlib's Locale on localizable Boolean algebras.
  • HStoneanLoc and HStonean. Morphisms are open frame maps (Definition 2.15) and open continuous maps. Hyperstonean spaces are sober spaces whose frame of opens is hyperstonean.
  • CVNA. Commutative CStarAlgebras with WStarAlgebra. Normality is stated as "pulls normal functionals back to normal functionals", which is equivalent to Definition 3.3 by Sakai's uniqueness of the predual.
  • No nontriviality. The empty space, the one-element Boolean algebra and the zero algebra are allowed.

The equivalence milestones assert an equivalence together with a description of its functor. They never take a functor as a hypothesis, so none of the statements reduces to rfl or to an instance argument.

Reusable parts:

  • the CSLEMS category, with the category laws of Propositions 4.7 and 4.14 proved inline;
  • the quotient M/NM/NM/N and the pull-back;
  • TM\mathrm{TM}TM and the Stone spectrum;
  • the projection Boolean algebra.

Contributions are welcome at every level: proofs of the milestones, Stone and Stonean duality for locales, and a lifting theorem.

Selected references

  • D. Pavlov, Gelfand-type duality for commutative von Neumann algebras, J. Pure Appl. Algebra 226 (2022); arXiv:2005.05284v3. https://arxiv.org/abs/2005.05284
  • J. Dixmier, Sur certains espaces considérés par M. H. Stone, Summa Brasil. Math. 2 (1951), 151–182.
  • M. H. Stone, Algebraic characterizations of special Boolean rings, Fund. Math. 29 (1937), 223–303. https://eudml.org/doc/212943
  • I. E. Segal, Equivalences of measure spaces, Amer. J. Math. 73 (1951), 275–313. https://doi.org/10.2307/2372178
  • D. Maharam, On a theorem of von Neumann, Proc. Amer. Math. Soc. 9 (1958), 987–994. https://doi.org/10.1090/S0002-9939-1958-0105479-6
  • D. H. Fremlin, Measure Theory, Vol. 3 (Measure algebras), Torres Fremlin, 2002.
  • P. T. Johnstone, Stone Spaces, Cambridge University Press, 1982.
  • S. Sakai, C*-algebras and W*-algebras, Springer, 1971.
22 thms3 active usersReviewed
ProbabilityQuantum InformationRandom Matrix Theory·Captain: mikedeng1

Asymptotics of random density matrices: The Rescaled Empirical Spectral Measure of an Induced Random Density Matrix Converges Almost Surely to the Marchenko–Pastur LawResearch Paper

Motivation

In quantum mechanics, a system that interacts with an environment is described by a density matrix: a positive semidefinite complex matrix of trace one. When nothing is known about the joint state of the system and its environment, a natural model is to take that joint state to be a uniformly random pure state and to trace out the environment. The resulting law on density matrices, the induced measure of Życzkowski and Sommers (Życzkowski–Sommers 2001), is a standard model of a "typical" mixed state. It is used in quantum information to study the typical entanglement of bipartite pure states, as in Page's conjecture on average entropy (Page 1993).

Nechita (arXiv:quant-ph/0702154v3, Ann. Henri Poincaré 2007) studies the asymptotics of this ensemble. In the regime where the system dimension nnn and the environment dimension k(n)k(n)k(n) grow proportionally, the spectrum of the random density matrix, magnified by cncncn, has the same almost sure limit as the spectrum of a Wishart matrix: the Marchenko–Pastur law (Marchenko–Pastur 1967). The mission formalizes this result (Theorem 5) together with the chain of statements the paper uses to derive it.

Setting

Throughout, NC(0,1)\mathcal N_{\mathbb C}(0,1)NC​(0,1) denotes the law of Z=X+iYZ = X + iYZ=X+iY where X,YX, YX,Y are independent real Gaussians of mean 000 and variance 1/21/21/2, so that E∣Z∣2=1\mathbb E|Z|^2 = 1E∣Z∣2=1.

  • Wishart matrix. If XXX is an n×kn \times kn×k complex matrix with i.i.d. NC(0,1)\mathcal N_{\mathbb C}(0,1)NC​(0,1) entries, W=XX∗W = XX^*W=XX∗ is a Wishart matrix of parameters nnn and kkk.
  • Pure states. A pure state of Cm\mathbb C^mCm is a ray ∣ψ⟩|\psi\rangle∣ψ⟩: a nonzero vector up to a nonzero scalar factor. Its pure density matrix is ∣ψ⟩⟨ψ∣=ψψ∗/∥ψ∥2|\psi\rangle\langle\psi| = \psi\psi^*/\|\psi\|^2∣ψ⟩⟨ψ∣=ψψ∗/∥ψ∥2, a rank-one orthogonal projection. The set EmE_mEm​ of pure states carries a unique probability measure νm\nu_mνm​ invariant under all unitaries U∈U(m)U \in U(m)U∈U(m).
  • Induced measure. Let H=Cn\mathcal H = \mathbb C^nH=Cn (the system) and K=Ck\mathcal K = \mathbb C^kK=Ck (the environment). If ∣ψ⟩|\psi\rangle∣ψ⟩ has law νnk\nu_{nk}νnk​ on the pure states of H⊗K\mathcal H\otimes\mathcal KH⊗K, the law of
ρ=Tr⁡K ∣ψ⟩⟨ψ∣\rho = \operatorname{Tr}_{\mathcal K}\,|\psi\rangle\langle\psi|ρ=TrK​∣ψ⟩⟨ψ∣

is the induced measure μn,k\mu_{n,k}μn,k​ on n×nn\times nn×n density matrices. Here Tr⁡K\operatorname{Tr}_{\mathcal K}TrK​ is the partial trace over the environment.

  • Empirical spectral measure. For an n×nn \times nn×n matrix AAA with eigenvalues λ1(A),…,λn(A)\lambda_1(A), \dots, \lambda_n(A)λ1​(A),…,λn​(A) (counted with multiplicity) and a scale sss, put Ls(A)=1n∑iδsλi(A)L^s(A) = \frac1n\sum_i \delta_{s\lambda_i(A)}Ls(A)=n1​∑i​δsλi​(A)​.
  • Marchenko–Pastur law. For c>0c > 0c>0, with a=(c−1)2a = (\sqrt c-1)^2a=(c​−1)2 and b=(c+1)2b = (\sqrt c+1)^2b=(c​+1)2,
μc=max⁡{1−c,0} δ0+(x−a)(b−x)2πx 1[a,b](x) dx.\mu_c = \max\{1-c,0\}\,\delta_0 + \frac{\sqrt{(x-a)(b-x)}}{2\pi x}\,\mathbf 1_{[a,b]}(x)\,dx .μc​=max{1−c,0}δ0​+2πx(x−a)(b−x)​​1[a,b]​(x)dx.

Formalization targets

Goal: Theorem 5 (p. 14)

Let c∈(0,∞)c \in (0,\infty)c∈(0,∞), let k(n)k(n)k(n) be integers with k(n)/n→ck(n)/n \to ck(n)/n→c, and let ρn\rho_nρn​ have law μn,k(n)\mu_{n,k(n)}μn,k(n)​ for every nnn. Then, almost surely,

Ln=1n∑i=1nδc n λi(ρn)  ⟹  μcweakly.L_n = \frac1n\sum_{i=1}^n \delta_{c\,n\,\lambda_i(\rho_n)} \;\Longrightarrow\; \mu_c \quad \text{weakly}.Ln​=n1​i=1∑n​δcnλi​(ρn​)​⟹μc​weakly.

Milestones, in the order the proof uses them

  1. Proposition 1 (p. 4): νn\nu_nνn​ exists and is unique.
  2. Proposition 2, item 1 (p. 4): the class of a vector with law NCn(0,In)\mathcal N^n_{\mathbb C}(0,I_n)NCn​(0,In​) has law νn\nu_nνn​.
  3. Eq. (12) (p. 6): if the coordinates ψij\psi_{ij}ψij​ are arranged in an n×kn \times kn×k matrix XXX, then Tr⁡K∣ψ⟩⟨ψ∣=XX∗/Tr⁡(XX∗)\operatorname{Tr}_{\mathcal K}|\psi\rangle\langle\psi| = XX^*/\operatorname{Tr}(XX^*)TrK​∣ψ⟩⟨ψ∣=XX∗/Tr(XX∗).
  4. Lemma 1 (p. 6): if XXX has i.i.d. NC(0,1)\mathcal N_{\mathbb C}(0,1)NC​(0,1) entries, then XX∗/Tr⁡(XX∗)XX^*/\operatorname{Tr}(XX^*)XX∗/Tr(XX∗) has law μn,k\mu_{n,k}μn,k​.
  5. Eq. (24) (p. 9): the eigenvalues of W/Tr⁡WW/\operatorname{Tr} WW/TrW are λi/∑jλj\lambda_i/\sum_j\lambda_jλi​/∑j​λj​.
  6. Theorem 2 (p. 8, quoted from Haagerup–Thorbjørnsen): almost surely, 1n∑iδn−1λi(Wn)⇒μc\frac1n\sum_i\delta_{n^{-1}\lambda_i(W_n)} \Rightarrow \mu_cn1​∑i​δn−1λi​(Wn​)​⇒μc​ for Wishart matrices WnW_nWn​ of parameters nnn and k(n)k(n)k(n).
  7. Lemma 2, (45) (p. 13): Tr⁡Wn/(n k(n))→1\operatorname{Tr} W_n/(n\,k(n)) \to 1TrWn​/(nk(n))→1 almost surely.
  8. The perturbation step (p. 14, eqs. (51)–(53)): dilating the atoms of a weakly convergent sequence by factors tn→1t_n \to 1tn​→1 does not change a compactly supported weak limit.

Significance

The result. Theorem 5 says that the reduced state of a large random bipartite pure state has a deterministic spectral profile at scale 1/(cn)1/(cn)1/(cn). When c<1c < 1c<1, the environment is smaller than the system, and an atom of mass 1−c1-c1−c at 000 records that ρn\rho_nρn​ has rank k(n)<nk(n) < nk(n)<n. When c≥1c \ge 1c≥1, the spectrum fills the interval [a,b][a, b][a,b]. The result transfers the classical Wishart limit to the induced measure, and with it quantitative information on the typical entanglement spectrum of bipartite pure states.

Formalizing it. The theorem is proved on paper, and none of it is machine-checked. The mission produces the induced-measure layer in Lean: complex Gaussian matrices, the invariant law on pure states, the partial-trace construction of μn,k\mu_{n,k}μn,k​, and the Marchenko–Pastur law with its atom. Lemma 1 and eq. (12) connect these objects to Wishart matrices. The step that needs the most new library is Theorem 2, the Marchenko–Pastur theorem itself, which the paper quotes without proof. The perturbation step is posed as a statement about weak convergence. The paper argues it through convergence of moments, and in that argument weak convergence of LnWL_n^WLnW​ is used as if it gave convergence of moments. The statement posed here is true as stated and needs no moment control.

Difficulty

The reduction from Theorem 5 to Theorem 2 is short on paper. The work lies elsewhere.

  • Theorem 2 is a full random-matrix limit theorem. It needs a method that identifies the limit (moments, Stieltjes transforms, or free probability) and concentration strong enough to give almost sure convergence with no coupling between different nnn.
  • Proposition 1 needs the invariant measure on complex projective space and a uniqueness argument for it. Mathlib's Haar-measure uniqueness is stated for groups, not for homogeneous spaces of U(n)U(n)U(n).
  • Lemma 1 needs the unitary invariance of the complex Gaussian vector NCnk(0,I)\mathcal N^{nk}_{\mathbb C}(0,I)NCnk​(0,I) and the image of a law under partial trace.

The naive route of "taking moments" in the perturbation step fails: weak convergence does not give convergence of moments, so (52)–(53) cannot be compared without extra tightness or moment bounds.

Formalization scope

  • Pure states. Rays of Cm\mathbb C^mCm are represented by their rank-one projections (IsPureDensity: Hermitian, idempotent, trace one). A law on EmE_mEm​ is a probability measure on m×mm\times mm×m complex matrices carried by that set. Unitary invariance is invariance under ρ↦UρU∗\rho \mapsto U\rho U^*ρ↦UρU∗ (IsPureStateLaw).
  • Induced law. "ρ\rhoρ has law μn,k\mu_{n,k}μn,k​" is the predicate HasInducedLaw: the law of ρ\rhoρ is the image under the partial trace of some unitarily invariant law on pure states of Cn⊗Ck\mathbb C^n\otimes\mathbb C^kCn⊗Ck. Proposition 1 makes this law unique.
  • Indexing and partial trace. Cn⊗Ck\mathbb C^n\otimes\mathbb C^kCn⊗Ck is indexed by Fin n × Fin k with the environment on the right. The partial trace is the published WildeQIT.partialTraceRight. NC(0,1)\mathcal N_{\mathbb C}(0,1)NC​(0,1) is the published SpikedWishart.SoftEdge.stdComplexGaussian, with variance 1/21/21/2 per real coordinate.
  • Eigenvalues and convergence. Eigenvalues are roots of the characteristic polynomial, counted with multiplicity. Weak convergence is ∫f dLn→∫f dμc\int f\,dL_n \to \int f\,d\mu_c∫fdLn​→∫fdμc​ for all bounded continuous fff, with one null set for all fff.
  • Disclosed conventions. The hypotheses hold for n≥1n \ge 1n≥1 with k(n)≥1k(n)\ge 1k(n)≥1, since there are no pure states in dimension 000. All random matrices live on one probability space, and nothing is assumed about their joint law across different nnn: the paper never couples them, and the almost sure statements hold for every coupling.
  • Trivializations ruled out. Three trivializing formalizations are excluded:
    • stating the law of ρn\rho_nρn​ through the Wishart formula Wn/Tr⁡WnW_n/\operatorname{Tr}W_nWn​/TrWn​, which would make Lemma 1 a hypothesis;
    • dropping the atom of μc\mu_cμc​ or leaving the limit measure free;
    • stating "for each fff, almost surely" in place of one null set for all fff.

Solvers are welcome to contribute in four places:

  • the general measure-theoretic pieces: Gaussian invariance, image laws under partial trace, and the dilation lemma, which are reusable beyond this mission;
  • the deterministic linear algebra of eqs. (12) and (24);
  • Lemma 2 through Borel–Cantelli;
  • any proof of Theorem 2.

Selected references

  • I. Nechita, Asymptotics of random density matrices, Ann. Henri Poincaré 8 (2007); arXiv:quant-ph/0702154v3. https://arxiv.org/abs/quant-ph/0702154v3
  • K. Życzkowski, H.-J. Sommers, Induced measures in the space of mixed quantum states, J. Phys. A 34 (2001) 7111–7125. https://doi.org/10.1088/0305-4470/34/35/335
  • U. Haagerup, S. Thorbjørnsen, Random matrices with complex Gaussian entries, Expo. Math. 21 (2003) 293–335. https://doi.org/10.1016/S0723-0869(03)80036-1
  • V. A. Marchenko, L. A. Pastur, Distribution of eigenvalues for some sets of random matrices, Math. USSR-Sb. 1 (1967) 457–483. https://doi.org/10.1070/SM1967v001n04ABEH001994
  • D. N. Page, Average entropy of a subsystem, Phys. Rev. Lett. 71 (1993) 1291–1294. https://doi.org/10.1103/PhysRevLett.71.1291
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Mathematical PhysicsQuantum InformationQuantum Mechanics·Captain: mikedeng1

Teleportation Stretching for Single-Mode Gaussian Channels: Exact LOCC Simulation of a Pure-Loss Channel from a Finite-Energy Effective Choi StateResearch Paper

Motivation

The ultimate rates of quantum communication over optical fibre — how many secret bits or entangled pairs per channel use a lossy line can carry with unlimited local operations and classical communication (LOCC) — are bounded through a technique called teleportation stretching (Pirandola, Laurenza, Ottaviani, Banchi, arXiv:1510.08863). The idea is that if a channel E\mathcal EE can be simulated by teleporting its input through a fixed resource state ρE\rho_{\mathcal E}ρE​, then any adaptive protocol using E\mathcal EE nnn times can be rewritten as LOCC acting on ρE⊗n\rho_{\mathcal E}^{\otimes n}ρE⊗n​, and every LOCC monotone of ρE\rho_{\mathcal E}ρE​ bounds the protocol's output.

For the pure-loss channel the natural resource is the Choi state I⊗Eη(ΦEPR)\mathcal I\otimes\mathcal E_\eta(\Phi_{\rm EPR})I⊗Eη​(ΦEPR​) of an ideal Einstein–Podolsky–Rosen state, which is not a normalizable state: it is the limit ξ→1\xi\to1ξ→1 of two-mode squeezed states and has infinite energy. R. Namiki (arXiv:1603.05292, 2016) observed that this limit can be avoided for lossy channels. Finite-squeezing teleportation, in the Braunstein–Kimble scheme (Braunstein and Kimble, PRL 80, 869, 1998), does not teleport perfectly, but its imperfection is itself a pure loss. Composing it with a second pure-loss channel therefore reproduces the target channel exactly, with a finite-energy resource.

Setting

A single bosonic mode is described on the Fock space ℓ2(N)\ell^2(\mathbb N)ℓ2(N) with number basis ∣n⟩|n\rangle∣n⟩. Every operator is handled through its number-basis kernel K(m,n)=⟨m∣X∣n⟩K(m,n)=\langle m|X|n\rangleK(m,n)=⟨m∣X∣n⟩; an operator on two modes has kernel K((r,b),(r′,b′))K((r,b),(r',b'))K((r,b),(r′,b′)), the first index labelling the first mode.

  • The displacement D(z)=eza†−zˉaD(z)=e^{za^\dagger-\bar z a}D(z)=eza†−zˉa, z∈Cz\in\mathbb Cz∈C, has explicit matrix entries ⟨m∣D(z)∣n⟩\langle m|D(z)|n\rangle⟨m∣D(z)∣n⟩; conjugation LD(z)(X)=D(z)XD(z)†\mathcal L_{D(z)}(X)=D(z)XD(z)^\daggerLD(z)​(X)=D(z)XD(z)† acts on kernels by matrix products.
  • The pure-loss channel Eη\mathcal E_\etaEη​, η∈(0,1)\eta\in(0,1)η∈(0,1), is the vacuum beam splitter of transmissivity η\etaη: a↦η aa\mapsto\sqrt\eta\,aa↦η​a with vacuum noise. I⊗Eη\mathcal I\otimes\mathcal E_\etaI⊗Eη​ applies it to the second mode.
  • The two-mode squeezed state with parameter ξ∈(0,1)\xi\in(0,1)ξ∈(0,1) is ∣ψξ⟩=1−ξ2∑n≥0ξn∣n⟩∣n⟩|\psi_\xi\rangle=\sqrt{1-\xi^2}\sum_{n\ge0}\xi^n|n\rangle|n\rangle∣ψξ​⟩=1−ξ2​∑n≥0​ξn∣n⟩∣n⟩ on modes (A′,B)(A',B)(A′,B).
  • The CV-Bell states are ∣Φβ⟩=(1⊗D†(β))∣Φ0⟩|\Phi_\beta\rangle=(\mathbb 1\otimes D^\dagger(\beta))|\Phi_0\rangle∣Φβ​⟩=(1⊗D†(β))∣Φ0​⟩ with ∣Φ0⟩=(2π)−1/2∑n∣n⟩∣n⟩|\Phi_0\rangle=(2\pi)^{-1/2}\sum_n|n\rangle|n\rangle∣Φ0​⟩=(2π)−1/2∑n​∣n⟩∣n⟩; they are improper vectors with ∬∣Φβ⟩⟨Φβ∣ dx dp=1\iint|\Phi_\beta\rangle\langle\Phi_\beta|\,dx\,dp=\mathbb 1∬∣Φβ​⟩⟨Φβ​∣dxdp=1, where β=(x+ip)/2\beta=(x+ip)/\sqrt2β=(x+ip)/2​.

Alice holds a two-mode state ρRS\rho_{RS}ρRS​ (SSS the signal, RRR a reference) and Alice and Bob share a resource ωA′B\omega_{A'B}ωA′B​. The unnormalized branch for outcome β\betaβ is the kernel on (R,B)(R,B)(R,B)

⟨Φβ∣SA′(ρ⊗ω)∣Φβ⟩SA′=12π∑n,n′,k,k′⟨n∣D(β)∣k⟩ ρ((⋅,n),(⋅,n′)) ω((k,⋅),(k′,⋅)) ⟨n′∣D(β)∣k′⟩‾.\langle\Phi_\beta|_{SA'}(\rho\otimes\omega)|\Phi_\beta\rangle_{SA'}=\frac1{2\pi}\sum_{n,n',k,k'}\langle n|D(\beta)|k\rangle\,\rho\big((\cdot,n),(\cdot,n')\big)\,\omega\big((k,\cdot),(k',\cdot)\big)\,\overline{\langle n'|D(\beta)|k'\rangle}.⟨Φβ​∣SA′​(ρ⊗ω)∣Φβ​⟩SA′​=2π1​n,n′,k,k′∑​⟨n∣D(β)∣k⟩ρ((⋅,n),(⋅,n′))ω((k,⋅),(k′,⋅))⟨n′∣D(β)∣k′⟩​.

Formalization targets

Goal: the Theorem (26)–(27), corrected protocol

For 0<η<ξ2<10<\eta<\xi^2<10<η<ξ2<1 put η′=η/ξ2\eta'=\eta/\xi^2η′=η/ξ2 and ρE′=I⊗Eη′(ψξ)\rho_{\mathcal E'}=\mathcal I\otimes\mathcal E_{\eta'}(\psi_\xi)ρE′​=I⊗Eη′​(ψξ​), the effective Choi state. For every two-mode density ρAB\rho_{AB}ρAB​,

I⊗Eη(ρAB)=∬R2L1⊗D(η′ξβˉ)(⟨Φβ∣SA′(ρAB⊗ρE′)∣Φβ⟩SA′) dx dp,\mathcal I\otimes\mathcal E_\eta(\rho_{AB})=\iint_{\mathbb R^2}\mathcal L_{\mathbb 1\otimes D(\sqrt{\eta'}\xi\bar\beta)}\Big(\langle\Phi_\beta|_{SA'}(\rho_{AB}\otimes\rho_{\mathcal E'})|\Phi_\beta\rangle_{SA'}\Big)\,dx\,dp ,I⊗Eη​(ρAB​)=∬R2​L1⊗D(η′​ξβˉ​)​(⟨Φβ​∣SA′​(ρAB​⊗ρE′​)∣Φβ​⟩SA′​)dxdp,

entry by entry, with every series and integral convergent, and η≤η′<1\eta\le\eta'<1η≤η′<1. The parameters and the protocol are independent of ρAB\rho_{AB}ρAB​.

Milestones

  1. (18) Displacement covariance: Eη(D(β)ρD†(β))=D(ηβ)Eη(ρ)D†(ηβ)\mathcal E_\eta(D(\beta)\rho D^\dagger(\beta))=D(\sqrt\eta\beta)\mathcal E_\eta(\rho)D^\dagger(\sqrt\eta\beta)Eη​(D(β)ρD†(β))=D(η​β)Eη​(ρ)D†(η​β) for every density.
  2. Composition (App. B): Eη∘Eη′=Eηη′\mathcal E_\eta\circ\mathcal E_{\eta'}=\mathcal E_{\eta\eta'}Eη​∘Eη′​=Eηη′​.
  3. (20), coherent input, corrected: ⟨Φβ∣(∣α⟩⟨α∣⊗ψξ)∣Φβ⟩=1−ξ22πe−(1−ξ2)∣α−βˉ∣2∣ξ(α−βˉ)⟩⟨ξ(α−βˉ)∣\langle\Phi_\beta|(|\alpha\rangle\langle\alpha|\otimes\psi_\xi)|\Phi_\beta\rangle=\frac{1-\xi^2}{2\pi}e^{-(1-\xi^2)|\alpha-\bar\beta|^2}|\xi(\alpha-\bar\beta)\rangle\langle\xi(\alpha-\bar\beta)|⟨Φβ​∣(∣α⟩⟨α∣⊗ψξ​)∣Φβ​⟩=2π1−ξ2​e−(1−ξ2)∣α−βˉ​∣2∣ξ(α−βˉ​)⟩⟨ξ(α−βˉ​)∣.
  4. (22), coherent input: the weights 1−ξ22πe−(1−ξ2)∣α−βˉ∣2\frac{1-\xi^2}{2\pi}e^{-(1-\xi^2)|\alpha-\bar\beta|^2}2π1−ξ2​e−(1−ξ2)∣α−βˉ​∣2 integrate to 111 over dx dpdx\,dpdxdp.
  5. (23), coherent input, corrected: after Eη\mathcal E_\etaEη​ the branch of milestone 3 becomes the same weight times ∣ηξ(α−βˉ)⟩⟨ηξ(α−βˉ)∣|\sqrt\eta\xi(\alpha-\bar\beta)\rangle\langle\sqrt\eta\xi(\alpha-\bar\beta)|∣η​ξ(α−βˉ​)⟩⟨η​ξ(α−βˉ​)∣.
  6. (24), every density, corrected: ∬D(ηξβˉ) Eη(Tβ,ξρTβ,ξ†) D†(ηξβˉ) dx dp=Eηξ2(ρ)\iint D(\sqrt\eta\xi\bar\beta)\,\mathcal E_\eta(T_{\beta,\xi}\rho T_{\beta,\xi}^\dagger)\,D^\dagger(\sqrt\eta\xi\bar\beta)\,dx\,dp=\mathcal E_{\eta\xi^2}(\rho)∬D(η​ξβˉ​)Eη​(Tβ,ξ​ρTβ,ξ†​)D†(η​ξβˉ​)dxdp=Eηξ2​(ρ).

Significance

The result. The Theorem shows that one use of a pure-loss channel, on any input including half of an entangled state, is reproduced exactly by LOCC on the finite-energy state I⊗Eη′(ψξ)\mathcal I\otimes\mathcal E_{\eta'}(\psi_\xi)I⊗Eη′​(ψξ​). In the paper's §II.C this is the step that would let entanglement-measure bounds for nnn adaptive channel uses be evaluated on a genuine density operator, without the limit ξ→1\xi\to1ξ→1 that the ideal-EPR argument needs. The relation (24) also makes precise in which sense the realistic teleportation family {Tβ,ξ}\{T_{\beta,\xi}\}{Tβ,ξ​} is not teleportation-stretching in the finite-dimensional sense, yet simulates the channel after an outcome-dependent displacement.

Formalizing it. The result is proved in the paper by a short computation through the Glauber–Sudarshan PPP representation, which is heuristic for nonclassical inputs. No machine-checked version exists. A formal proof requires an argument valid for every density operator, together with all convergence statements. The formalization also records a sign slip: with the paper's own definitions (4), (16), (A4) and D(β)=eβa†−β∗aD(\beta)=e^{\beta a^\dagger-\beta^*a}D(β)=eβa†−β∗a, the step ⟨α∗∣D(β)=⟨α∗+β∗∣\langle\alpha^*|D(\beta)=\langle\alpha^*+\beta^*|⟨α∗∣D(β)=⟨α∗+β∗∣ in (20) should read ⟨α∗−β∣\langle\alpha^*-\beta|⟨α∗−β∣. Consequently (20) and (23) hold with α−βˉ\alpha-\bar\betaα−βˉ​ in place of α+β\alpha+\betaα+β, and the correction in (24) is D(ηξβˉ)D(\sqrt\eta\xi\bar\beta)D(η​ξβˉ​) rather than D†(ηξβ)D^\dagger(\sqrt\eta\xi\beta)D†(η​ξβ); a numerical evaluation of the printed (24) for the input 0.6∣0⟩+0.8i∣1⟩0.6|0\rangle+0.8i|1\rangle0.6∣0⟩+0.8i∣1⟩ gives an error of 0.380.380.38 in the output matrix, against 8×10−58\times10^{-5}8×10−5 (grid-limited) for the corrected one. The Theorem itself, existential in the protocol, is unaffected.

Difficulty

The obvious route is the paper's: write ρ=∫Pα∣α⟩⟨α∣ d2α\rho=\int P_\alpha|\alpha\rangle\langle\alpha|\,d^2\alphaρ=∫Pα​∣α⟩⟨α∣d2α, compute everything for coherent states, and integrate. For nonclassical states PPP is not a function, or even a measure, so this route is not a proof; passing from coherent inputs to all densities needs a density or continuity argument in trace norm, with interchange of the outcome integral and the infinite Fock series. The Bell projection itself is a contraction against improper vectors, here encoded as an absolutely convergent four-fold series whose convergence for arbitrary trace-class inputs is part of the work. Finally, the composition Eη∘Eη′=Eηη′\mathcal E_\eta\circ\mathcal E_{\eta'}=\mathcal E_{\eta\eta'}Eη​∘Eη′​=Eηη′​ and the covariance (18) are standard on covariance matrices but must be established on number-basis kernels, where they are identities between infinite series with binomial weights.

Formalization scope

  • Representation. All states and outputs are number-basis kernels. Inputs are bounded operators on ℓ2(N)\ell^2(\mathbb N)ℓ2(N) or ℓ2(N×N)\ell^2(\mathbb N\times\mathbb N)ℓ2(N×N) satisfying the published density predicates (trace class, self-adjoint, positive, unit trace), from QAlgorithms_Papers_Independent_Dependency50_P39; the loss channel is the vacuum-loss kernel of QAlgorithms_Papers_Independent_Frontier30_P21; coherent states use its coherentDensity.
  • Bell projection. It is the Fock form of (16) with (A4), with the factor (2π)−1(2\pi)^{-1}(2π)−1 explicit; the CV-Bell states are not formalized as vectors. The outcome is β=(x+ip)/2\beta=(x+ip)/\sqrt2β=(x+ip)/2​ and the average is over R×R\mathbb R\times\mathbb RR×R with Lebesgue measure, the paper's dx dpdx\,dpdxdp.
  • Conventions. The resource has Alice's mode A′A'A′ first and Bob's mode BBB second; the loss of ρE′\rho_{\mathcal E'}ρE′​ acts on BBB. Every series is asserted summable and every integrand integrable as part of the conclusion, so default values of divergent series or non-integrable functions never satisfy a statement.
  • Corrected sign. Milestones (20), (23), (24) and the goal use α−βˉ\alpha-\bar\betaα−βˉ​ and the correction D(η′ξβˉ)D(\sqrt{\eta'}\xi\bar\beta)D(η′​ξβˉ​), as explained above.
  • Coherent-input restriction. Milestones (20), (22), (23) are stated for coherent inputs (PPP a point mass), because the PPP representation (19) is not available for general states; (24) and the goal are stated for every density, as printed.
  • LOCC. The general class of LOCC maps is not formalized; Λ\LambdaΛ is the explicit protocol of (24). An existential "there is a map Λ\LambdaΛ with Λ(ρE′)=I⊗Eη(ρAB)\Lambda(\rho_{\mathcal E'})=\mathcal I\otimes\mathcal E_\eta(\rho_{AB})Λ(ρE′​)=I⊗Eη​(ρAB​)" would be trivially true (take Λ\LambdaΛ constant) and is ruled out by stating the protocol, with η′\eta'η′, ξ\xiξ and the correction fixed before ρAB\rho_{AB}ρAB​; likewise the Bell branch is the defining series, never its closed form.
  • Not covered. The thermal-loss and amplifier versions (§III, (30)–(33)), the nnn-use relative-entropy bound (§II.C), and the finite-dimensional review (§II.A). The statement Eη(∣α⟩⟨α∣)=∣ηα⟩⟨ηα∣\mathcal E_\eta(|\alpha\rangle\langle\alpha|)=|\sqrt\eta\alpha\rangle\langle\sqrt\eta\alpha|Eη​(∣α⟩⟨α∣)=∣η​α⟩⟨η​α∣ used inside (20) is the existing Open goal Frontier30.P21.coherentOutput and is not posed again.
  • Reusable parts. Proofs of displacement covariance and of channel composition on Fock kernels, and summability lemmas for displacement matrices against trace-class kernels, are useful beyond this mission; contributions of such lemmas are welcome.

Selected references

  • R. Namiki, Teleportation stretching for single-mode Gaussian channels, arXiv:1603.05292v1, 2016. https://arxiv.org/abs/1603.05292
  • S. Pirandola, R. Laurenza, C. Ottaviani, L. Banchi, Fundamental limits of repeaterless quantum communications, arXiv:1510.08863v3, 2015. https://arxiv.org/abs/1510.08863
  • S. L. Braunstein, H. J. Kimble, Teleportation of continuous quantum variables, Phys. Rev. Lett. 80, 869, 1998. https://doi.org/10.1103/PhysRevLett.80.869
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Mathematical PhysicsQuantum Information·Captain: mikedeng1

Preparation of Entangled States by Quantum Markov Processes: Every n-Qubit Pure State Is the Unique and Attractive Stationary State of a Dissipative Process with Relaxation Time 1/min_k g_kResearch Paper

Motivation

Quantum technologies usually prepare a desired state by isolating a system and driving it with carefully timed unitary operations; coupling to an environment is treated as noise. Dissipative state preparation reverses this view: one engineers the system–environment coupling so that the open-system dynamics itself drives every initial state into a prescribed target state. Because the target is a fixed point that attracts all initial conditions, the preparation needs no initialization and is self-correcting against perturbations that leave the dynamics unchanged.

In 2008 three closely related papers made this programme concrete. Diehl, Micheli, Kantian, Kraus, Büchler and Zoller showed how cold atoms can be driven into condensed many-body states by engineered dissipation (arXiv:0803.1482); Verstraete, Wolf and Cirac showed that dissipative dynamics can perform universal quantum computation and prepare matrix product and PEPS states (arXiv:0803.1447); and Kraus, Büchler, Diehl, Kantian, Micheli and Zoller, Preparation of entangled states by quantum Markov processes (arXiv:0803.1463), gave the general uniqueness criteria and the explicit construction this mission formalizes. The last paper's central claim is that every pure state of nnn qubits is the unique stationary state of an explicitly given Markovian process, and that this process relaxes on a time scale independent of nnn.

Setting

A quantum Markov process on a ddd-dimensional Hilbert space is a master equation ρ˙=L(ρ)\dot\rho = \mathcal L(\rho)ρ˙​=L(ρ) for a density matrix ρ\rhoρ (a positive semidefinite d×dd\times dd×d complex matrix of trace one). In the paper's Eq. (2) the generator, or Liouvillian, is

LH,cl(ρ)=−i[H,ρ]+∑lgl(2clρcl†−cl†clρ−ρcl†cl),\mathcal L_{H,c_l}(\rho) = -i[H,\rho] + \sum_l g_l\bigl(2c_l\rho c_l^\dagger - c_l^\dagger c_l\rho - \rho c_l^\dagger c_l\bigr),LH,cl​​(ρ)=−i[H,ρ]+l∑​gl​(2cl​ρcl†​−cl†​cl​ρ−ρcl†​cl​),

where HHH is a Hermitian matrix (the Hamiltonian), the clc_lcl​ are arbitrary complex matrices (the jump operators) and glg_lgl​ are rates. The solution is ρ(t)=etL(ρ(0))\rho(t) = e^{t\mathcal L}(\rho(0))ρ(t)=etL(ρ(0)). The paper writes P=∑lglcl†clP = \sum_l g_l c_l^\dagger c_lP=∑l​gl​cl†​cl​, Q=P−iHQ = P - iHQ=P−iH and E(ρ)=2∑lglclρcl†\mathcal E(\rho) = 2\sum_l g_l c_l\rho c_l^\daggerE(ρ)=2∑l​gl​cl​ρcl†​.

A stationary state is a density matrix with L(ρ)=0\mathcal L(\rho) = 0L(ρ)=0. A vector annihilated by every clc_lcl​ and an eigenvector of HHH is a dark vector; the set D=K(P)∩ES(H)D = K(P)\cap ES(H)D=K(P)∩ES(H) of dark vectors, when it is a subspace (all dark vectors share one eigenvalue EEE of HHH), yields the dark states, the density matrices with range inside DDD.

For nnn qubits, σ−(k)=1⊗⋯⊗∣0⟩k⟨1∣⊗⋯⊗1\sigma_-^{(k)} = \mathbb 1\otimes\dots\otimes|0\rangle_k\langle1|\otimes\dots\otimes\mathbb 1σ−(k)​=1⊗⋯⊗∣0⟩k​⟨1∣⊗⋯⊗1 lowers qubit kkk from ∣1⟩|1\rangle∣1⟩ to ∣0⟩|0\rangle∣0⟩. Given any unitary UUU, the target is ∣Ψ⟩=U∣0n⟩|\Psi\rangle = U|0^n\rangle∣Ψ⟩=U∣0n⟩, which ranges over all pure states, and the construction of §IV uses the nnn jump operators ck=Uσ−(k)U†c_k = U\sigma_-^{(k)}U^\daggerck​=Uσ−(k)​U† with rates gkg_kgk​. The relaxation time TrelaxT_{\mathrm{relax}}Trelax​ is the inverse of the least value of −Re⁡μ-\operatorname{Re}\mu−Reμ over the nonzero eigenvalues μ\muμ of L\mathcal LL.

Formalization targets

Goal: unique, attractive, and fast

For n≥1n\ge1n≥1, any unitary UUU and rates g1,…,gn>0g_1,\dots,g_n>0g1​,…,gn​>0:

(a)∀H=H† with H∣Ψ⟩=E∣Ψ⟩:LH,ck(ρ)=0, ρ a density matrix  ⟺  ρ=∣Ψ⟩⟨Ψ∣;\text{(a)}\quad \forall H = H^\dagger \text{ with } H|\Psi\rangle = E|\Psi\rangle:\qquad \mathcal L_{H,c_k}(\rho) = 0,\ \rho \text{ a density matrix} \iff \rho = |\Psi\rangle\langle\Psi|;(a)∀H=H† with H∣Ψ⟩=E∣Ψ⟩:LH,ck​​(ρ)=0, ρ a density matrix⟺ρ=∣Ψ⟩⟨Ψ∣; (b)etL{ck}(ρ)→t→∞∣Ψ⟩⟨Ψ∣ for every density matrix ρ;(c)Trelax=1min⁡kgk.\text{(b)}\quad e^{t\mathcal L_{\{c_k\}}}(\rho)\xrightarrow[t\to\infty]{}|\Psi\rangle\langle\Psi| \text{ for every density matrix } \rho;\qquad \text{(c)}\quad T_{\mathrm{relax}} = \frac{1}{\min_k g_k}.(b)etL{ck​}​(ρ)t→∞​∣Ψ⟩⟨Ψ∣ for every density matrix ρ;(c)Trelax​=mink​gk​1​.

Clause (a) allows every Hamiltonian that has the target as an eigenvector; (b) and (c) concern the purely dissipative process H=0H = 0H=0, the one the paper solves explicitly.

Milestones

  1. Dark states are stationary (§II, p. 2).
  2. Theorem 1 (p. 2): L(∣Φ⟩⟨Φ∣)=0\mathcal L(|\Phi\rangle\langle\Phi|) = 0L(∣Φ⟩⟨Φ∣)=0 iff Q†∣Φ⟩=λ∣Φ⟩Q^\dagger|\Phi\rangle = \lambda|\Phi\rangleQ†∣Φ⟩=λ∣Φ⟩ and cl∣Φ⟩=λl∣Φ⟩c_l|\Phi\rangle = \lambda_l|\Phi\ranglecl​∣Φ⟩=λl​∣Φ⟩ with ∑lgl∣λl∣2=Re⁡λ\sum_l g_l|\lambda_l|^2 = \operatorname{Re}\lambda∑l​gl​∣λl​∣2=Reλ.
  3. D′=DD' = DD′=D (p. 3, footnote [35]): Q†ψ=iλψQ^\dagger\psi = i\lambda\psiQ†ψ=iλψ with λ\lambdaλ real iff ψ\psiψ is dark.
  4. Theorem 2 (p. 3): if no nonzero subspace S⊥DS\perp DS⊥D satisfies clS⊆Sc_lS\subseteq Scl​S⊆S for all lll, the only stationary states are the dark states.
  5. Dark vectors of {ck}\{c_k\}{ck​} (§IV, p. 4): ckφ=0c_k\varphi = 0ck​φ=0 for all kkk iff φ∈C∣Ψ⟩\varphi\in\mathbb C|\Psi\rangleφ∈C∣Ψ⟩.
  6. The monomial claim (§IV, p. 4): for χ⊥∣0n⟩\chi\perp|0^n\rangleχ⊥∣0n⟩, χ≠0\chi\ne0χ=0, some product PPP of the σ−(k)\sigma_-^{(k)}σ−(k)​ has ⟨0n∣P∣χ⟩≠0\langle0^n|P|\chi\rangle\ne0⟨0n∣P∣χ⟩=0.
  7. Unitary covariance (§IV.A, p. 4): L{Uσ−(k)U†}(σ)=UL{σ−(k)}(U†σU)U†\mathcal L_{\{U\sigma_-^{(k)}U^\dagger\}}(\sigma) = U\mathcal L_{\{\sigma_-^{(k)}\}}(U^\dagger\sigma U)U^\daggerL{Uσ−(k)​U†}​(σ)=UL{σ−(k)​}​(U†σU)U†.
  8. One qubit (§IV.A, p. 4): eigenvalues 0,−2g,−g,−g0, -2g, -g, -g0,−2g,−g,−g on ∣0⟩⟨0∣,σz,σx,σy|0\rangle\langle0|, \sigma_z, \sigma_x, \sigma_y∣0⟩⟨0∣,σz​,σx​,σy​.
  9. Product spectrum (§IV.A, p. 4): the explicit operators U(σi1(1)⊗⋯⊗σin(n))U†U(\sigma_{i_1}^{(1)}\otimes\cdots\otimes\sigma_{i_n}^{(n)})U^\daggerU(σi1​(1)​⊗⋯⊗σin​(n)​)U† form an eigenbasis, with eigenvalues ∑kλik\sum_k\lambda_{i_k}∑k​λik​​; these are exactly −∑kmkgk-\sum_k m_kg_k−∑k​mk​gk​, mk∈{0,1,2}m_k\in\{0,1,2\}mk​∈{0,1,2}.

Significance

The result. The goal shows that dissipative preparation is universal for pure states: no pure state, however entangled, is out of reach, and the required jump operators are written down explicitly. Clause (c) states that the time to reach the target is governed by the weakest single coupling and does not grow with the number of qubits. Theorems 1 and 2 are general tools independent of the construction: Theorem 1 characterizes every pure stationary state of every Lindblad generator, and Theorem 2 is a checkable sufficient condition for the absence of other stationary states. The later sections of the paper (stabilizer and graph states, PEPS and the AKLT state, a driven condensate, the η\etaη-condensate) apply these tools to physically local processes.

Formalizing it. The results are classical and proved in the paper, partly in sketched form ("straightforward", "the same arguments as above"). No machine-checked proof of any of them is known. The formalization supplies complete arguments for the sketched steps, fixes the guards the printed statements omit (listed below), and produces a reusable layer of statements about the spectrum and stationary states of Lindblad generators on finite-dimensional spaces.

Difficulty

The first idea for uniqueness is to show that the target is the only pure stationary state, using Theorem 1. That is not enough: a Lindblad generator can have mixed stationary states even when its pure stationary state is unique (with Hermitian jump operators the maximally mixed state is always stationary, Eq. (4)). Excluding mixed stationary states is the content of Theorem 2, whose proof requires a positivity argument for Q†ρ+ρQQ^\dagger\rho + \rho QQ†ρ+ρQ and a decomposition of ρ\rhoρ along D⊕D⊥D\oplus D^\perpD⊕D⊥.

For convergence, uniqueness of the stationary state does not suffice either: a purely imaginary eigenvalue would make etL(ρ)e^{t\mathcal L}(\rho)etL(ρ) oscillate forever. Clauses (b) and (c) need the full spectrum of the 4n4^n4n-dimensional Liouvillian, obtained by reducing to U=1U = \mathbb 1U=1 and decoupling into nnn single-qubit problems; in Lean this means relating the eigenvalues of a generator on 2n×2n2^n\times 2^n2n×2n matrices to those of tensor factors.

Formalization scope

The generator, the semigroup etLe^{t\mathcal L}etL (matrix exponential of the Liouvillian as a linear map), and the predicates stationary (density matrix with Lρ=0\mathcal L\rho = 0Lρ=0), attractive and lazy (nonzero subspace invariant under all jump operators) are reused from the published definition QAlgorithms_Papers_Independent_Dependency50_P16. That layer normalizes the dissipator as ∑kVkρVk†−12{Vk†Vk,ρ}\sum_k V_k\rho V_k^\dagger - \frac12\{V_k^\dagger V_k,\rho\}∑k​Vk​ρVk†​−21​{Vk†​Vk​,ρ}; the paper's rates enter through jump operators Vl=2gl clV_l = \sqrt{2g_l}\,c_lVl​=2gl​​cl​, which reproduces Eq. (2) exactly. Operators are complex d×dd\times dd×d matrices, states are vectors in Cd\mathbb C^dCd, and nnn qubits are indexed by {0,…,2n−1}\{0,\dots,2^n-1\}{0,…,2n−1} with qubit 1 the most significant bit; ∣0n⟩|0^n\rangle∣0n⟩ is the basis vector of index 000. Density matrices are positive semidefinite of trace one, and ∣ψ⟩⟨ψ∣|\psi\rangle\langle\psi|∣ψ⟩⟨ψ∣ is formed without normalization, so unit norm is assumed where the paper says "state". Convergence is entrywise.

Conventions added to the paper and disclosed in each statement:

  • rates gl>0g_l>0gl​>0 (the paper allows gℓ≥0g_\ell\ge0gℓ​≥0; with a zero rate Theorem 1 and uniqueness fail);
  • Theorem 2 quantifies over nonzero subspaces (the zero subspace would make its hypothesis unsatisfiable), and keeps the standing assumption that DDD is a subspace, as a fixed eigenvalue EEE;
  • n≥1n\ge1n≥1 in clause (c); the relaxation rate is a least element and must be positive before its reciprocal is a finite relaxation time;
  • "∣φ⟩=U∣0n⟩|\varphi\rangle = U|0^n\rangle∣φ⟩=U∣0n⟩" is read up to a scalar, and the single-qubit "iff σi∈Σk\sigma_i\in\Sigma_kσi​∈Σk​" as four eigen-equations.

A trivializing formalization is ruled out: the target is not fixed to U=1U = \mathbb 1U=1, the jump operators are the conjugated Uσ−(k)U†U\sigma_-^{(k)}U^\daggerUσ−(k)​U† and not σ−(k)\sigma_-^{(k)}σ−(k)​, clause (a) quantifies over all Hamiltonians with the target as eigenvector rather than only H=0H = 0H=0, and the relaxation time refers to the actual nonzero spectrum of the generator.

A complete development needs: properties of the Lindblad generator under unitary conjugation; positivity arguments for completely positive maps on matrices; the tensor-product structure of 2n×2n2^n\times 2^n2n×2n matrices over qubit wires; and the spectrum and diagonalizability of a sum of commuting single-site generators. The spectral and stationary-state lemmas are reusable for any finite-dimensional open-system mission. Contributions to any milestone, and alternative proofs of Theorem 2 or of the spectrum, are welcome.

Selected references

  • B. Kraus, H. P. Büchler, S. Diehl, A. Kantian, A. Micheli, P. Zoller, Preparation of entangled states by quantum Markov processes, Phys. Rev. A 78 (2008); arXiv:0803.1463v3. https://arxiv.org/abs/0803.1463
  • S. Diehl, A. Micheli, A. Kantian, B. Kraus, H. P. Büchler, P. Zoller, Quantum states and phases in driven open quantum systems with cold atoms, Nature Physics 4 (2008). https://arxiv.org/abs/0803.1482
  • F. Verstraete, M. M. Wolf, J. I. Cirac, Quantum computation and quantum-state engineering driven by dissipation, Nature Physics 5 (2009). https://arxiv.org/abs/0803.1447
  • E. Malvetti et al., Reachability, coolability, and stabilizability of open Markovian quantum systems with fast unitary control, 2023; arXiv:2308.00561. https://arxiv.org/abs/2308.00561
  • G. Lindblad, On the generators of quantum dynamical semigroups, Comm. Math. Phys. 48 (1976). https://doi.org/10.1007/BF01608499
  • V. Gorini, A. Kossakowski, E. C. G. Sudarshan, Completely positive dynamical semigroups of N-level systems, J. Math. Phys. 17 (1976). https://doi.org/10.1063/1.522979
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Dynamical SystemsMathematical PhysicsProbability+1·Captain: mikedeng1

Entropic Fluctuations in Statistical Mechanics I. Classical Dynamical Systems: Finite-Time Green–Kubo Formula and Onsager Reciprocity from the Generalized Evans–Searles SymmetryResearch Paper

Motivation

In a system driven away from equilibrium, a force changes a reference state and a dynamics, while a corresponding flux records the transported quantity. Statistical mechanics asks how the mean flux changes under a small force. A second question is whether the matrix of these changes is symmetric when the underlying dynamics admit time reversal. Jakšić, Pillet and Rey-Bellet derive both answers at a fixed, finite observation time from a generalized Evans–Searles fluctuation symmetry for classical dynamical systems in their 2010 preprint, §4. This finite-time statement does not require a large-time limit, a stationary nonequilibrium state, or an asymptotic fluctuation theorem.

The paper first develops the entropy cocycle and its time-reversal properties for a single system. Its Proposition 3.3 gives a scalar finite-time Evans–Searles identity. Section 4 lets the dynamics and reference state depend on a vector of forces and introduces a vector of fluxes. Proposition 4.6, the target here, is the section’s stated finite-time Green–Kubo and Onsager result Jakšić, Pillet and Rey-Bellet, pp. 18–21.

Setting

Fix a positive integer NNN and a measurable configuration space MMM. Each force vector X∈RNX\in\mathbb R^NX∈RN determines a continuous-time measurable flow ϕXs:M→M\phi_X^s:M\to MϕXs​:M→M, a probability state ωX\omega_XωX​, and an entropy-production observable σX\sigma_XσX​. The evolved states of each system are equivalent to ωX\omega_XωX​, and the regularity assumption (E1) makes σX\sigma_XσX​ the derivative of the evolved-state density in L1(ωX)L^1(\omega_X)L1(ωX​). The family also has a measurable flux vector ΦX=(ΦX(1),…,ΦX(N))\Phi_X=(\Phi_X^{(1)},\ldots,\Phi_X^{(N)})ΦX​=(ΦX(1)​,…,ΦX(N)​) satisfying the flux relation σX=X⋅ΦX\sigma_X=X\cdot\Phi_XσX​=X⋅ΦX​ almost everywhere. These are the family and flux conventions of §4.1 Jakšić, Pillet and Rey-Bellet, pp. 17–18.

At equilibrium, X=0X=0X=0. Assumption (T1) says only that ω0\omega_0ω0​ is invariant under ϕ0s\phi_0^sϕ0s​; no stationarity is imposed on ωX\omega_XωX​ for nonzero XXX. Assumption (T2) gives each XXX-system a possibly different time reversal ϑX\vartheta_XϑX​ preserving ωX\omega_XωX​, reversing the flow, and sending ΦX\Phi_XΦX​ to −ΦX-\Phi_X−ΦX​ almost everywhere. For t>0t>0t>0, the XXX-system time average is

⟨ΦX(j)⟩t=1t∫0tωX(ΦX(j)∘ϕXs) ds,\langle\Phi_X^{(j)}\rangle_t=\frac1t\int_0^t\omega_X(\Phi_X^{(j)}\circ\phi_X^s)\,ds,⟨ΦX(j)​⟩t​=t1​∫0t​ωX​(ΦX(j)​∘ϕXs​)ds,

and its force derivative at equilibrium is Ljkt=∂Xk⟨ΦX(j)⟩t∣X=0L_{jkt}=\left.\partial_{X_k}\langle\Phi_X^{(j)}\rangle_t\right|_{X=0}Ljkt​=∂Xk​​⟨ΦX(j)​⟩t​​X=0​. The equilibrium correlation with indices j,kj,kj,k is Cjk(s)=ω0(Φ0(k)(Φ0(j)∘ϕ0s))C_{jk}(s)=\omega_0(\Phi_0^{(k)}(\Phi_0^{(j)}\circ\phi_0^s))Cjk​(s)=ω0​(Φ0(k)​(Φ0(j)​∘ϕ0s​)). Thus the time-shifted factor carries index jjj.

The generalized Evans–Searles functional is the log-Laplace transform of the actual integrated flux,

gt(X,Y)=log⁡ωX ⁣(exp⁡[−Y⋅∫0tΦX∘ϕXs ds]),g_t(X,Y)=\log\omega_X\!\left(\exp\left[-Y\cdot\int_0^t\Phi_X\circ\phi_X^s\,ds\right]\right),gt​(X,Y)=logωX​(exp[−Y⋅∫0t​ΦX​∘ϕXs​ds]),

with extended real values when the exponential moment diverges. Proposition 4.3 states gt(X,Y)=gt(X,X−Y)g_t(X,Y)=g_t(X,X-Y)gt​(X,Y)=gt​(X,X−Y) under (T1)–(T2) Jakšić, Pillet and Rey-Bellet, p. 19.

Formalization targets

Generalized finite-time symmetry

Proposition 4.2 relates the law PXtP_X^tPXt​ of the averaged flux to its reflection PˉXt\bar P_X^tPˉXt​ for nonzero ttt: dPˉXt/dPXt(s)=e−tX⋅sd\bar P_X^t/dP_X^t(s)=e^{-tX\cdot s}dPˉXt​/dPXt​(s)=e−tX⋅s. Proposition 4.3 states the equivalent symmetry of gtg_tgt​. Lemma 4.4 is a calculus statement about a C1,2C^{1,2}C1,2 function with that symmetry. These are the three new numbered milestones; the earlier entropy-cocycle results, Propositions 3.1, 3.2 and 3.8, are reused as published references Jakšić, Pillet and Rey-Bellet, pp. 8–12, 19.

Finite-time response

The goal is all of Proposition 4.6, at each fixed t>0t>0t>0:

X↦⟨ΦX⟩t is differentiable at 0,Ljkt=12∫−ttCjk(s)(1−∣s∣t)ds,Ljkt=Lkjt.X\mapsto\langle\Phi_X\rangle_t\text{ is differentiable at }0,\qquad L_{jkt}=\frac12\int_{-t}^{t}C_{jk}(s)\left(1-\frac{|s|}{t}\right)ds,\qquad L_{jkt}=L_{kjt}.X↦⟨ΦX​⟩t​ is differentiable at 0,Ljkt​=21​∫−tt​Cjk​(s)(1−t∣s∣​)ds,Ljkt​=Lkjt​.

The first clause is the paper’s assumption (T3) as a conclusion. The second is the finite-time Green–Kubo formula and the third the finite-time Onsager reciprocity relation Jakšić, Pillet and Rey-Bellet, pp. 20–21.

Significance

The formula determines the first-order response matrix from correlations measured entirely in the equilibrium system. Its triangular weight records a finite observation window. Reciprocity then says that cross-responses agree after exchanging the flux and force coordinates. Both statements are exact at fixed time, so they can be used before an asymptotic transport coefficient is known to exist Jakšić, Pillet and Rey-Bellet, Proposition 4.6 and Remarks 1–2, pp. 20–21.

The paper proves these claims. The formalization task is to express and eventually verify the known result, including the dependent family of states and flows, the extended log moment, and all three clauses of the proposition. The published §3 definitions and cocycle statements provide a reusable base. A checked §4 development would also expose general measure and calculus lemmas for finite-time fluctuation relations. At drafting, these new statements compile as open Lean theorems; compilation does not supply their proofs.

Difficulty

The symmetry is an equality of potentially infinite log moments, while the response matrix uses real derivatives near the origin. Local finiteness must justify passage between those two regimes. The paper’s C1,2C^{1,2}C1,2 convention includes five families of continuous partial derivatives, including both orders of mixed differentiation, but does not demand two XXX derivatives. Treating it as ordinary C2C^2C2 would change the theorem.

There is also a measure-theoretic gap between a time integral of fluxes inside an expectation and an integral of expectations over time. A formal statement must control that interchange and the two-time correlation integral. Stationarity is available only at equilibrium, although both the state and flow vary with XXX in the response derivative. The one-line formula for ⟨f⟩t\langle f\rangle_t⟨f⟩t​ on p. 20 leaves its state implicit; the first display of the proof on p. 21 and the entropy balance used in (4.30) identify it as the XXX-system state for f=ΦXf=\Phi_Xf=ΦX​ Jakšić, Pillet and Rey-Bellet, pp. 20–21.

Formalization scope

The Lean family uses RN\mathbb R^NRN as Fin N → ℝ with N>0N>0N>0, a measurable type MMM, and one published RegularSystem M for each XXX. That type supplies (F1), (F2), (C), and (E1); the new family supplies the flux relation and almost-everywhere time integrability of each coordinate on finite intervals, so the paper's integrated flux is defined. Observable identities in the flux relation and time reversal are ωX\omega_XωX​-almost everywhere. The law PXtP_X^tPXt​ is the pushforward of ωX\omega_XωX​ under the integrated flux divided by ttt. The log-Laplace transform uses a nonnegative integral and EReal, retaining +∞+\infty+∞; a real conversion occurs only on a neighborhood where finiteness is stated.

The goal requires t>0t>0t>0, since its triangular kernel and time average refer to [0,t][0,t][0,t]. Proposition 4.2 requires t≠0t\ne0t=0 because PXtP_X^tPXt​ otherwise contains a division by zero; Proposition 4.3 includes t=0t=0t=0. To make the correlation and Fubini steps meaningful, equilibrium flux coordinates are assumed in L2(ω0)L^2(\omega_0)L2(ω0​) and the XXX-system flux is locally integrable on [0,t]×M[0,t]\times M[0,t]×M near X=0X=0X=0. These are labeled analytic hypotheses, not new physical symmetry assumptions. Coordinate partials are derivatives along coordinate lines, with existence as well as continuity asserted for the five families on an open neighborhood.

The target uses the actual log-Laplace transform and the force derivative of the actual time average. It imposes stationarity only at X=0X=0X=0, uses equilibrium correlations, and keeps precisely C1,2C^{1,2}C1,2 regularity. The family interface and the calculus and integration lemmas needed to prove the milestones are reusable; contributions that close any of the numbered milestones or the analytic interchange obligations fit this scope.

Selected references

  • V. Jakšić, C.-A. Pillet and L. Rey-Bellet, Entropic Fluctuations in Statistical Mechanics I. Classical Dynamical Systems, arXiv preprint arXiv:1009.3248v2, 2010. Preprint.
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Harmonic AnalysisRandom Matrix TheoryRepresentation Theory·Captain: mikedeng1

The Weingarten Calculus: Haar Integrals of Matrix Elements Are Given by a Basis of Invariant Tensors and Its Weingarten Matrix, I = A W A*Research Paper

Motivation

Integrals of polynomial functions of the matrix entries of a random element of a compact group appear across mathematical physics and probability: in random matrix theory (moments of Haar-distributed unitary, orthogonal and symplectic matrices), in lattice gauge theory (the link integrals of U(N)U(N)U(N) gauge fields), and in quantum information (averages of quantum channels over random unitaries, twirling, unitary designs). Weingarten first computed asymptotics of such integrals for U(N)U(N)U(N) in 1978 (Weingarten, J. Math. Phys. 19 (1978)); Collins (IMRN 2003) and Collins–Śniady (CMP 2006) gave exact formulas for the unitary, orthogonal and symplectic groups in terms of what is now called the Weingarten function.

The survey of Collins, Matsumoto and Novak, The Weingarten Calculus (arXiv:2109.14890), isolates the single statement underneath all these formulas, valid for every compact group and every finite-dimensional unitary representation. This mission formalizes that statement, Theorem 2.1 of the survey, together with the steps of its proof as written in Section 2.

Setting

Let GGG be a compact Hausdorff topological group and μ\muμ its Haar probability measure, the unique Borel probability measure on GGG invariant under left translation. Let H=CNH=\mathbb{C}^NH=CN with its standard orthonormal basis e1,…,eNe_1,\dots,e_Ne1​,…,eN​, and let U:G→U(N)U:G\to\mathrm U(N)U:G→U(N) be a continuous group homomorphism into the unitary N×NN\times NN×N matrices. Its matrix elements are Uxy(g)=⟨ex,U(g)ey⟩U_{xy}(g)=\langle e_x,U(g)e_y\rangleUxy​(g)=⟨ex​,U(g)ey​⟩, the (x,y)(x,y)(x,y) entry of U(g)U(g)U(g).

Fix d∈Nd\in\mathbb Nd∈N. A multi-index is a function i:[d]→[N]i:[d]\to[N]i:[d]→[N]; the set of them is Fun(d,N)\mathrm{Fun}(d,N)Fun(d,N). The Weingarten integrals of degree ddd are

Iij=∫G∏x=1dUi(x)j(x)(g) dμ(g),i,j∈Fun(d,N).I_{ij}=\int_G\prod_{x=1}^d U_{i(x)j(x)}(g)\,d\mu(g),\qquad i,j\in\mathrm{Fun}(d,N).Iij​=∫G​x=1∏d​Ui(x)j(x)​(g)dμ(g),i,j∈Fun(d,N).

The tensor power H⊗dH^{\otimes d}H⊗d has the orthonormal basis ei=ei(1)⊗⋯⊗ei(d)e_i=e_{i(1)}\otimes\cdots\otimes e_{i(d)}ei​=ei(1)​⊗⋯⊗ei(d)​, and the tensor-power matrix U⊗d(g)U^{\otimes d}(g)U⊗d(g) has entries Uij⊗d(g)=∏x=1dUi(x)j(x)(g)U^{\otimes d}_{ij}(g)=\prod_{x=1}^dU_{i(x)j(x)}(g)Uij⊗d​(g)=∏x=1d​Ui(x)j(x)​(g). The invariant tensors are

(H⊗d)G={t∈H⊗d:U⊗d(g) t=t for all g∈G},(H^{\otimes d})^G=\{t\in H^{\otimes d}: U^{\otimes d}(g)\,t=t\ \text{for all }g\in G\},(H⊗d)G={t∈H⊗d:U⊗d(g)t=t for all g∈G},

and the Haar average is the matrix P=∫GU⊗d(g) dμ(g)P=\int_GU^{\otimes d}(g)\,d\mu(g)P=∫G​U⊗d(g)dμ(g). Given vectors a1,…,am∈H⊗da_1,\dots,a_m\in H^{\otimes d}a1​,…,am​∈H⊗d, let A=[⟨ei,ax⟩]A=[\langle e_i,a_x\rangle]A=[⟨ei​,ax​⟩] be the Nd×mN^d\times mNd×m matrix whose columns are their coordinates, A∗A^*A∗ its conjugate transpose, A∗A=[⟨ax,ay⟩]A^*A=[\langle a_x,a_y\rangle]A∗A=[⟨ax​,ay​⟩] their Gram matrix, and, when it is invertible, W=(A∗A)−1W=(A^*A)^{-1}W=(A∗A)−1 the Weingarten matrix of a1,…,ama_1,\dots,a_ma1​,…,am​.

Formalization targets

Goal: Theorem 2.1 (p. 4)

If a1,…,ama_1,\dots,a_ma1​,…,am​ is a basis of (H⊗d)G(H^{\otimes d})^G(H⊗d)G, then for all i,j∈Fun(d,N)i,j\in\mathrm{Fun}(d,N)i,j∈Fun(d,N)

Iij=∑x,y=1mAix Wxy Ayj∗.I_{ij}=\sum_{x,y=1}^mA_{ix}\,W_{xy}\,A^*_{yj}.Iij​=x,y=1∑m​Aix​Wxy​Ayj∗​.

The identity is exact and holds for every compact group, every continuous unitary representation, every degree ddd and every choice of basis; nothing is fixed beyond the data.

Milestones (Section 2, pp. 3–4)

  1. Iij=PijI_{ij}=P_{ij}Iij​=Pij​: the Weingarten integrals are the matrix elements of the Haar average.
  2. P∗=PP^*=PP∗=P, P2=PP^2=PP2=P, and im⁡P=(H⊗d)G\operatorname{im}P=(H^{\otimes d})^GimP=(H⊗d)G: PPP is the orthogonal projection onto the invariant tensors (the existing platform theorem that a Haar average of a compact group representation is an idempotent fixing exactly the invariant vectors is included as a supporting reference item).
  3. For linearly independent columns, the selfadjoint idempotent with image span⁡{ax}\operatorname{span}\{a_x\}span{ax​} is A(A∗A)−1A∗A(A^*A)^{-1}A^*A(A∗A)−1A∗.

Significance

Theorem 2.1 reduces a family of analytic problems — Haar integrals of polynomials in matrix entries — to two algebraic ones: find a basis of the invariant tensors of GGG in H⊗dH^{\otimes d}H⊗d (classical invariant theory), and invert its Gram matrix. For U(N)U(N)U(N) the invariants come from Schur–Weyl duality and the Weingarten matrix becomes the Weingarten function on permutations; for O(N)O(N)O(N) and Sp(N)Sp(N)Sp(N) the invariants are indexed by pair partitions; for the symmetric group S(N)S(N)S(N) acting by permutation matrices the invariants are indicators of set partitions. Each of these case-specific formulas, surveyed in Sections 3–5 of the paper, is an instance of Theorem 2.1, so a formal proof of the theorem is the common entry point for formalizing any of them.

The theorem is classical and its proof is elementary once stated; it is not open. No machine-checked proof is known to exist in Mathlib or on this platform: Mathlib has Haar measure, unitary groups and Gram matrices (including the equivalence of linear independence with invertibility of the Gram matrix), but not the averaging projection of a representation in matrix form nor the formula A(A∗A)−1A∗A(A^*A)^{-1}A^*A(A∗A)−1A∗ for orthogonal projections. The mission produces both as reusable lemmas and the Fundamental Theorem itself.

Difficulty

The argument is short on paper; the formal work sits in three places. First, selfadjointness of PPP needs ∫GF(g−1) dμ=∫GF(g) dμ\int_GF(g^{-1})\,d\mu=\int_GF(g)\,d\mu∫G​F(g−1)dμ=∫G​F(g)dμ, i.e. unimodularity of a compact group, which Mathlib does not provide as an instance for non-commutative groups. Second, identifying the image of PPP with the invariant tensors needs both directions: invariant vectors are fixed by PPP, and every vector PtPtPt is invariant, which uses left invariance of μ\muμ inside a matrix-valued Bochner integral. Third, the projection formula needs invertibility of A∗AA^*AA∗A from linear independence and an argument that a selfadjoint idempotent is determined by its image. Commuting the integral with matrix entries and products is routine but must be done with care for the matrix norm chosen.

Formalization scope

  • HHH is CN\mathbb C^NCN with its standard basis (a finite-dimensional Hilbert space with a specified orthonormal basis is the same thing after identification); UUU is a monoid homomorphism G →* Matrix.unitaryGroup (Fin N) ℂ, assumed continuous. Indices are 0-based: [N][N][N] is Fin N, multi-indices are Fin d → Fin N, tensors are (Fin d → Fin N) → ℂ.
  • GGG carries [IsTopologicalGroup G] [CompactSpace G] [T2Space G] [BorelSpace G], and μ\muμ is a Haar measure that is a probability measure. Right invariance is not assumed; it is a consequence that solvers must prove.
  • ddd ranges over all of N\mathbb NN, including d=0d=0d=0, where both sides equal 111; the paper takes ddd positive.
  • The inner product is conjugate-linear in the first slot, so Ayj∗=Ajy‾A^*_{yj}=\overline{A_{jy}}Ayj∗​=Ajy​​ and A∗A^*A∗ is Mathlib's conjugate transpose.
  • PPP is a Bochner integral of matrices, taken with the entrywise sup norm; in finite dimension the integral is independent of the norm.
  • The basis hypothesis is two hypotheses: LinearIndependent ℂ a and span (range a) = invariants U d, with the invariant subspace defined from the representation. Without independence Mathlib's matrix inverse returns 000 on a singular Gram matrix, and the statement would be false; it is therefore not a trivializing gap but a necessary hypothesis.
  • Correction. The paper says "a basis a1,…,ama_1,\dots,a_ma1​,…,am​ of (H)⊗d(H)^{\otimes d}(H)⊗d"; the same paragraph calls the axa_xax​ "the basic invariants", and with a basis of all of H⊗dH^{\otimes d}H⊗d the right-hand side would be the identity. The formal statement uses a basis of (H⊗d)G(H^{\otimes d})^G(H⊗d)G.
  • A trivializing formalization — defining the Weingarten integral as AWA∗AWA^*AWA∗, defining the invariant space as the image of PPP, or assuming that PPP projects onto the span of the axa_xax​ — is excluded: the left side is the Haar integral of the product of matrix elements written out, and the invariant space is defined by U⊗d(g)t=tU^{\otimes d}(g)t=tU⊗d(g)t=t.

Needed infrastructure: matrix-valued Bochner integrals commuting with entries and with matrix multiplication; unimodularity of compact groups; the orthogonal-projection formula. All three are reusable well beyond this mission, and contributions of these general lemmas are welcome.

Selected references

  • B. Collins, S. Matsumoto, J. Novak, The Weingarten Calculus, arXiv preprint, 2021. https://arxiv.org/abs/2109.14890
  • D. Weingarten, Asymptotic behavior of group integrals in the limit of infinite rank, J. Math. Phys. 19 (1978), 999–1001. https://doi.org/10.1063/1.523807
  • B. Collins, Moments and cumulants of polynomial random variables on unitary groups, the Itzykson–Zuber integral, and free probability, Int. Math. Res. Not. 2003, no. 17, 953–982. https://doi.org/10.1155/S107379280320917X
  • B. Collins, P. Śniady, Integration with respect to the Haar measure on unitary, orthogonal and symplectic group, Comm. Math. Phys. 264 (2006), 773–795. https://doi.org/10.1007/s00220-006-1554-3
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