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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.

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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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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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EconomicsOperations ResearchProbability·Captain: mikedeng1

Ranking Distributions When Only Means and Variances Are Known: Y Dominates X by First-Order Almost Stochastic Dominance for γ ≥ 1/(1 + 2t(t + √(t² + 1))), t = (μ_Y − μ_X)/(σ_Y + σ_X)Research Paper

Motivation

Decision analysts routinely have to rank two risky prospects, with returns XXX and YYY, when nothing is known about them beyond a mean and a standard deviation for each. The classical tools are of two kinds. First-order stochastic dominance (FSD) ranks YYY above XXX for every increasing utility, but it can never be certified from means and variances alone: with only the first two moments fixed, the admissible laws of XXX and YYY include pairs that FSD does not rank. Mean–variance rules such as the Sharpe ratio rank everything, but lack a general expected-utility justification. Müller, Scarsini, Tsetlin and Winkler (Ranking distributions when only means and variances are known, Operations Research 69(3), 2021; SSRN 3440103) close the gap by restricting the utilities: they bound the ratio of marginal utilities, and they ask how strong that bound must be for every pair of laws with the given moments to be ranked.

The relevant order between the two extremes is almost first-order stochastic dominance (AFSD), introduced by Leshno and Levy (Management Science, 2002) to rule out "pathological" utilities that FSD must accommodate. Müller, Scarsini, Tsetlin and Winkler (Management Science, 2017) discuss that this symmetric case of their order is AFSD, i.e. the order generated by utilities whose marginal utilities differ at most by a fixed factor. Leshno and Levy computed the smallest parameter for which one given pair of laws is ranked; the present mission concerns a bound that holds for all pairs with prescribed means and variances.

Setting

Fix γcv,γcx∈R\gamma_{cv},\gamma_{cx}\in\mathbb Rγcv​,γcx​∈R. The utility class Uγcv,γcx\mathcal U_{\gamma_{cv},\gamma_{cx}}Uγcv​,γcx​​ consists of continuously differentiable u:R→Ru:\mathbb R\to\mathbb Ru:R→R with

0≤γcv u′(y)≤u′(x)and0≤γcx u′(x)≤u′(y)for all x≤y.0\le\gamma_{cv}\,u'(y)\le u'(x)\quad\text{and}\quad0\le\gamma_{cx}\,u'(x)\le u'(y)\qquad\text{for all }x\le y.0≤γcv​u′(y)≤u′(x)and0≤γcx​u′(x)≤u′(y)for all x≤y.

For 0≤γcv,γcx≤10\le\gamma_{cv},\gamma_{cx}\le10≤γcv​,γcx​≤1 and real random variables X,YX,YX,Y, YYY dominates XXX by (1+γcv,1+γcx)(1+\gamma_{cv},1+\gamma_{cx})(1+γcv​,1+γcx​)-SD, written X≤(1+γcv,1+γcx)YX\le_{(1+\gamma_{cv},1+\gamma_{cx})}YX≤(1+γcv​,1+γcx​)​Y, if E u(X)≤E u(Y)\mathbb E\,u(X)\le\mathbb E\,u(Y)Eu(X)≤Eu(Y) for every u∈Uγcv,γcxu\in\mathcal U_{\gamma_{cv},\gamma_{cx}}u∈Uγcv​,γcx​​. The symmetric case γcv=γcx=γ\gamma_{cv}=\gamma_{cx}=\gammaγcv​=γcx​=γ is ε\varepsilonε-AFSD with ε=γ/(1+γ)\varepsilon=\gamma/(1+\gamma)ε=γ/(1+γ): γ=0\gamma=0γ=0 gives FSD, and γ=1\gamma=1γ=1 gives the increasing affine utilities, i.e. ranking by means. Increasing γ\gammaγ shrinks Uγ,γ\mathcal U_{\gamma,\gamma}Uγ,γ​ and makes the order easier to satisfy.

Write μX,μY\mu_X,\mu_YμX​,μY​ for the means and σX,σY\sigma_X,\sigma_YσX​,σY​ for the standard deviations, and

t=μY−μXσY+σX,γ∗=11+2t(t+t2+1).t=\frac{\mu_Y-\mu_X}{\sigma_Y+\sigma_X},\qquad \gamma^*=\frac{1}{1+2t\big(t+\sqrt{t^2+1}\big)}.t=σY​+σX​μY​−μX​​,γ∗=1+2t(t+t2+1​)1​.

The quantity ttt is a standardized advantage of YYY over XXX; γ∗\gamma^*γ∗ decreases from 111 at t=0t=0t=0 towards 000 as t→∞t\to\inftyt→∞.

The proof works with the piecewise-linear utilities uU(x;δ)=γ(x−δ)+(1−γ)(x−δ)+u_U(x;\delta)=\gamma(x-\delta)+(1-\gamma)(x-\delta)_+uU​(x;δ)=γ(x−δ)+(1−γ)(x−δ)+​ and uL(x;δ)=γ(x−δ)−(1−γ)(δ−x)+u_L(x;\delta)=\gamma(x-\delta)-(1-\gamma)(\delta-x)_+uL​(x;δ)=γ(x−δ)−(1−γ)(δ−x)+​, with x+=max⁡{x,0}x_+=\max\{x,0\}x+​=max{x,0}, and with the closed forms

B(γ,δ)=γ(μX−δ)+(1−γ)12(μX−δ+σX2+(μX−δ)2),A(γ,δ)=γ(μY−δ)−(1−γ)12(δ−μY+σY2+(μY−δ)2),B(\gamma,\delta)=\gamma(\mu_X-\delta)+(1-\gamma)\tfrac12\Big(\mu_X-\delta+\sqrt{\sigma_X^2+(\mu_X-\delta)^2}\Big),\quad A(\gamma,\delta)=\gamma(\mu_Y-\delta)-(1-\gamma)\tfrac12\Big(\delta-\mu_Y+\sqrt{\sigma_Y^2+(\mu_Y-\delta)^2}\Big),B(γ,δ)=γ(μX​−δ)+(1−γ)21​(μX​−δ+σX2​+(μX​−δ)2​),A(γ,δ)=γ(μY​−δ)−(1−γ)21​(δ−μY​+σY2​+(μY​−δ)2​),

the paper's worst-case values of E uU(X;δ)\mathbb E\,u_U(X;\delta)EuU​(X;δ) and E uL(Y;δ)\mathbb E\,u_L(Y;\delta)EuL​(Y;δ) given the moments, and the point δ∗=(μXσY+μYσX)/(σY+σX)\delta^*=(\mu_X\sigma_Y+\mu_Y\sigma_X)/(\sigma_Y+\sigma_X)δ∗=(μX​σY​+μY​σX​)/(σY​+σX​).

Formalization targets

Goal: Theorem 7 (p. 6)

For square-integrable X,YX,YX,Y with μY>μX\mu_Y>\mu_XμY​>μX​,

γ∗≤γ≤1 ⟹ X≤(1+γ,1+γ)Y.\gamma^*\le\gamma\le1\ \Longrightarrow\ X\le_{(1+\gamma,1+\gamma)}Y.γ∗≤γ≤1 ⟹ X≤(1+γ,1+γ)​Y.

The goal quantifies over all X,YX,YX,Y with the given moments; nothing about their laws is fixed. The upper bound γ≤1\gamma\le1γ≤1 is the domain of the order in Definition 1(b).

Milestones (proof of Theorem 7, pp. 6–8)

  1. Every v∈Uγ,γv\in\mathcal U_{\gamma,\gamma}v∈Uγ,γ​ with 0<γ≤10<\gamma\le10<γ≤1 is a u+ba\,u+bau+b with a≥0a\ge0a≥0, u(δ)=0u(\delta)=0u(δ)=0 and γ≤u′≤1\gamma\le u'\le1γ≤u′≤1.
  2. Such a uuu satisfies uL(x;δ)≤u(x)≤uU(x;δ)u_L(x;\delta)\le u(x)\le u_U(x;\delta)uL​(x;δ)≤u(x)≤uU​(x;δ).
  3. Lemma 4 (Scarf's bound) E X+≤12(μ+σ2+μ2)\mathbb E\,X_+\le\frac12\big(\mu+\sqrt{\sigma^2+\mu^2}\big)EX+​≤21​(μ+σ2+μ2​) — already proved on the platform as PricingRM.DetHeuristic.gallego_bound (the case C=0C=0C=0).
  4. E uU(X;δ)≤B(γ,δ)\mathbb E\,u_U(X;\delta)\le B(\gamma,\delta)EuU​(X;δ)≤B(γ,δ) and 5. E uL(Y;δ)≥A(γ,δ)\mathbb E\,u_L(Y;\delta)\ge A(\gamma,\delta)EuL​(Y;δ)≥A(γ,δ).
  5. f(−t)2t+f(−t)=−t+1+t2t+1+t2=γ∗\dfrac{f(-t)}{2t+f(-t)}=\dfrac{-t+\sqrt{1+t^2}}{t+\sqrt{1+t^2}}=\gamma^*2t+f(−t)f(−t)​=t+1+t2​−t+1+t2​​=γ∗, with f(z)=z+1+z2f(z)=z+\sqrt{1+z^2}f(z)=z+1+z2​.
  6. A(γ,δ∗)≥B(γ,δ∗)A(\gamma,\delta^*)\ge B(\gamma,\delta^*)A(γ,δ∗)≥B(γ,δ∗) for all γ≥γ∗\gamma\ge\gamma^*γ≥γ∗.
  7. δ∗\delta^*δ∗ is the unique minimizer of h(δ)=σYf(δ−μYσY)+σXf(μX−δσX)h(\delta)=\sigma_Y f\big(\frac{\delta-\mu_Y}{\sigma_Y}\big)+\sigma_X f\big(\frac{\mu_X-\delta}{\sigma_X}\big)h(δ)=σY​f(σY​δ−μY​​)+σX​f(σX​μX​−δ​) for σX,σY>0\sigma_X,\sigma_Y>0σX​,σY​>0.

Significance

The result. Theorem 7 turns two summary statistics into an expected-utility guarantee: once (μY−μX)/(σY+σX)(\mu_Y-\mu_X)/(\sigma_Y+\sigma_X)(μY​−μX​)/(σY​+σX​) exceeds the value making γ∗≤γ\gamma^*\le\gammaγ∗≤γ, every decision maker whose marginal utility varies by at most the factor 1/γ1/\gamma1/γ prefers YYY, concave or not. It complements the paper's Theorems 3 and 6, which restrict to concave and to convex utilities and give tight bounds in (μY−μX)/σY(\mu_Y-\mu_X)/\sigma_Y(μY​−μX​)/σY​ and (μY−μX)/σX(\mu_Y-\mu_X)/\sigma_X(μY​−μX​)/σX​; the class Uγ,γ\mathcal U_{\gamma,\gamma}Uγ,γ​ contains utilities that are neither, and both standard deviations enter. The paper's Example 8 shows the practical use: with γ=0.37\gamma=0.37γ=0.37 the rule "t>0.53t>0.53t>0.53" settles a project choice for a whole team with heterogeneous, non-concave preferences. The authors note that the bound of Theorem 7 is not tight; the tight constant is open in the paper (Remarks 9–10).

Formalizing it. The result is proved in the paper; none of it is formalized. A formal development produces a reusable definition of the bounded-marginal-utility-ratio class and of AFSD in Mathlib's probability language, distribution-free bounds on expectations of piecewise-linear functions of a square-integrable variable, and a machine-checked version of the threshold. The Scarf/Gallego bound, which the proof uses twice, is already proved on the platform.

Difficulty

The obvious argument fails at the first step: a stochastic dominance relation is usually checked through distribution functions, but nothing about the distribution functions of XXX and YYY is known. For concave utilities (Theorem 3) Jensen's inequality disposes of XXX entirely, which is why that bound ignores σX\sigma_XσX​; for the symmetric class no such step is available, both variables must be controlled at once, and the worst case over all laws with given moments must be computed in closed form for a family of utilities rather than for a single one. On the formal side, the normalization step needs the boundedness of u′u'u′ to be derived from the ratio condition (there is no supremum hypothesis), the bounds need integrability of u(X)u(X)u(X) for an unbounded uuu, and the threshold computation is real algebra with nested square roots.

Formalization scope

Random variables are measurable functions X,Y:Ω→RX,Y:\Omega\to\mathbb RX,Y:Ω→R on one probability space (Ω,P)(\Omega,P)(Ω,P), with MemLp X 2 P and MemLp Y 2 P in the goal; only their laws matter. Means are Bochner integrals and σX=Var⁡X\sigma_X=\sqrt{\operatorname{Var}X}σX​=VarX​ with Mathlib's variance, never free reals in the goal. "Continuously differentiable" is ContDiff ℝ 1 and u′u'u′ is deriv u. The order SDle carries 0≤γcv,γcx≤10\le\gamma_{cv},\gamma_{cx}\le10≤γcv​,γcx​≤1 and integrability of XXX and YYY, because the identity utility is in the class. It compares the expectations for every utility in the class for which both compositions are integrable. This excludes Lean's zero value for a non-integrable integral from a comparison, while keeping the order reflexive when γ=0\gamma=0γ=0; every class utility is integrable under the goal's hypotheses. Divisions follow Lean's a/0=0a/0=0a/0=0; when σX=σY=0\sigma_X=\sigma_Y=0σX​=σY​=0 the paper's ttt is undefined, Lean gives t=0t=0t=0 and γ∗=1\gamma^*=1γ∗=1, and the goal then asserts dominance for increasing affine utilities only, which is true. The worst-case quantities BBB and AAA are stated as the inequalities the proof uses; attainment (the two-point laws) is not formalized.

A trivializing formalization is ruled out: the goal is stated for every uuu in the class, not only for uU,uLu_U,u_LuU​,uL​ or at a fixed δ\deltaδ; for every pair X,YX,YX,Y with the moments as hypotheses, not for chosen laws; and with γ≤1\gamma\le1γ≤1, since for γ>1\gamma>1γ>1 the class contains only constants.

A complete development needs: the mean value inequality for deriv; integrability of Lipschitz functions of an L2L^2L2 variable; the Gallego bound (available); and elementary real algebra with Real.sqrt. The utility class, the order, and the bounds on E uU\mathbb E\,u_UEuU​, E uL\mathbb E\,u_LEuL​ are reusable for Theorems 3 and 6 of the same paper and for other almost-dominance results. Proofs of any milestone, alternative proofs of the goal, and formalizations of Theorems 3 and 6 are welcome.

Selected references

  • A. Müller, M. Scarsini, I. Tsetlin, R. L. Winkler, Ranking distributions when only means and variances are known, Operations Research 69(3), 2021; INSEAD Working Paper 2020/36/DSC, 2020. https://ssrn.com/abstract=3440103
  • A. Müller, M. Scarsini, I. Tsetlin, R. L. Winkler, Between first- and second-order stochastic dominance, Management Science 63(9):2933–2947, 2017.
  • M. Leshno, H. Levy, Preferred by "all" and preferred by "most" decision makers: almost stochastic dominance, Management Science 48(8):1074–1085, 2002.
  • H. Scarf, A min-max solution of an inventory problem, in K. J. Arrow, S. Karlin, H. Scarf (eds.), Studies in the Mathematical Theory of Inventory and Production, pp. 201–209, Stanford University Press, 1958.
  • J. R. Birge, J. H. Dulá, Bounding separable recourse functions with limited distribution information, Annals of Operations Research 30:277–298, 1991.
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🏆Completed
EconomicsOperations Research·Captain: mikedeng1

Curbing Emissions: Environmental Regulations and Product Offerings Across Markets: Horizontal Negotiation Unifies a Split Market at the Exact Global Standard and Lowers Total EmissionsResearch Paper

Motivation

Energy-efficiency and emission standards for products such as vehicles and appliances are set by regulators whose jurisdictions overlap a single manufacturer's markets. The best-known case is United States fuel-economy regulation. California has long been allowed to set stricter vehicle standards than the federal government, and the 2019 dispute between California and the federal administration over a single "50-state" standard put the question of split versus unified markets on the policy agenda. A manufacturer facing two different standards can sell two product versions (a split market), sell one version that meets the stricter standard everywhere (a unified market), or withdraw from the stricter market.

Han, Hu and Dawande (Curbing Emissions: Environmental Regulations and Product Offerings Across Markets, Manufacturing & Service Operations Management, 2022) model this as a game between an environmentally concerned regulator, an environmentally agnostic regulator, and a monopolist. They ask when the market splits, and whether negotiation between the regulators can unify a split market and lower total emissions. This mission formalizes their answer for one negotiation format, the exact global standard (§4.1.1), together with the base-model results it rests on. Citations refer to the authors' accepted manuscript of 28 July 2022, including its Online Appendices.

Setting

A monopolist sells in two markets M1,M2M_1, M_2M1​,M2​ of sizes m1,m2>0m_1, m_2 > 0m1​,m2​>0. Regulator RiR_iRi​ sets a minimum efficiency standard si≥0s_i \ge 0si​≥0 for products sold in MiM_iMi​. Consumers' valuations are uniform on [0,uˉ][0, \bar u][0,uˉ]. A consumer with valuation uuu who buys a product of efficiency eee at price ppp receives u−p+γeu - p + \gamma eu−p+γe, where γ\gammaγ is the efficiency bonus, and buys when this is positive. Producing efficiency eee costs cec ece per unit plus a fixed setup cost r>0r > 0r>0 per product.

Regulator R1R_1R1​ maximizes consumer utility in M1M_1M1​ minus h1∑i(b−ei)⋅salesih_1 \sum_i (b - e_i)\cdot\text{sales}_ih1​∑i​(b−ei​)⋅salesi​. Here bbb is a benchmark efficiency, h1h_1h1​ is the perceived per-unit environmental impact, and the sum runs over both markets. Regulator R2R_2R2​ maximizes consumer utility in M2M_2M2​ only and therefore sets s2=0s_2 = 0s2​=0. The total emissions are ∑i(b−ei)⋅salesi\sum_i (b - e_i)\cdot\text{sales}_i∑i​(b−ei​)⋅salesi​.

Given s1s_1s1​, the firm chooses among three strategies: DDD (differentiated products at s1s_1s1​ and 000), UUU (one unified product at s1s_1s1​ in both markets), and SSS (one product at 000, sold in M2M_2M2​ only). Each product is priced at p∗=[(c+γ)e+uˉ]/2p^* = [(c+\gamma)e + \bar u]/2p∗=[(c+γ)e+uˉ]/2. A base-model outcome is a standard s1≥0s_1 \ge 0s1​≥0 together with a profit-maximizing strategy of the firm, such that R1R_1R1​ cannot do better with another standard paired with any profit-maximizing response.

In the exact-standard negotiation, R1R_1R1​ and R2R_2R2​ agree on one standard ses_ese​ for both markets and a transfer tht_hth​ from R1R_1R1​ to R2R_2R2​. Their total utility is Th(se)T_h(s_e)Th​(se​) (eq. (4)). The disagreement point (D1,D2)(D_1, D_2)(D1​,D2​) is the pair of utilities at the split-market base outcome, and the negotiated pair maximizes the Nash product (Π1−D1)(Π2−D2)(\Pi_1 - D_1)(\Pi_2 - D_2)(Π1​−D1​)(Π2​−D2​) over the feasible pairs that split the gain equally.

Formalization targets

Goal: Proposition 3 (p. 19)

Assume condition (1) of Lemma A.1, where xˉ\bar xxˉ is the larger root of an auxiliary quadratic:

0<r≤min⁡{m2uˉ4−m2[uˉ−b(c−γ)]2uˉ(4−c−γh1)2, m1[uˉ−b(c−γ)]2uˉ(4−c−γh1)2, m24uˉ(uˉ2−xˉ2)}.0<r\le\min\Big\{\tfrac{m_2\bar u}{4}-\tfrac{m_2[\bar u-b(c-\gamma)]^2}{\bar u(4-\frac{c-\gamma}{h_1})^2},\ \tfrac{m_1[\bar u-b(c-\gamma)]^2}{\bar u(4-\frac{c-\gamma}{h_1})^2},\ \tfrac{m_2}{4\bar u}(\bar u^2-\bar x^2)\Big\}.0<r≤min{4m2​uˉ​−uˉ(4−h1​c−γ​)2m2​[uˉ−b(c−γ)]2​, uˉ(4−h1​c−γ​)2m1​[uˉ−b(c−γ)]2​, 4uˉm2​​(uˉ2−xˉ2)}.

Then a split-market base outcome (s1,D)(s_1, D)(s1​,D) exists. For every such outcome, the negotiation has a Nash bargaining solution, and every solution has standard

se∗=2h1[uˉ+b(c−γ)]−(c−γ)uˉ(c−γ)[4h1−(c−γ)].s^*_e=\frac{2h_1[\bar u+b(c-\gamma)]-(c-\gamma)\bar u}{(c-\gamma)[4h_1-(c-\gamma)]}.se∗​=(c−γ)[4h1​−(c−γ)]2h1​[uˉ+b(c−γ)]−(c−γ)uˉ​.

The regulators' total utility at se∗s^*_ese∗​ strictly exceeds D1+D2D_1 + D_2D1​+D2​, and total emissions at se∗s^*_ese∗​ are strictly lower than at the split-market outcome.

Milestones

  1. The optimal price p∗p^*p∗ (§3.1, p. 12).
  2. Lemma 1 (p. 12): the firm's best response is UUU for s1≤τUs_1 \le \tau_Us1​≤τU​, DDD for τU≤s1≤τS\tau_U \le s_1 \le \tau_SτU​≤s1​≤τS​, and SSS for s1≥τSs_1 \ge \tau_Ss1​≥τS​.
  3. The constant xˉ\bar xxˉ is well defined (proof of Lemma A.1, Online Appendix p. 12).
  4. Lemma A.1(1): under condition (1), (s1D∗,D)(s^*_{1D}, D)(s1D∗​,D) is a base-model outcome, and every split outcome has s1=s1D∗s_1 = s^*_{1D}s1​=s1D∗​.
  5. The arbitrator's optimal standard sa∗s^*_asa∗​ for eq. (3) (p. 16).
  6. The reduction of the Nash bargaining solution to maximizing ThT_hTh​ (§4.1.1, p. 19).
  7. The closed-form gain Th(se∗)−D1−D2T_h(s^*_e) - D_1 - D_2Th​(se∗​)−D1​−D2​ (proof of Proposition 3, Online Appendix p. 13).
  8. Proposition 2, split-market half (p. 16): a split outcome emits more than the arbitrator outcome.

Significance

The result. Proposition 3 shows that, whenever the base model predicts a split market under the paper's sufficient condition, two regulators who negotiate an exact global standard with side payments always reach agreement. The agreed standard unifies the market and lowers total emissions. The negotiated standard coincides with the standard a neutral arbitrator would choose. This makes the exact global standard the benchmark against which the paper compares its other negotiation formats (a baseline global standard, and vertical negotiation with the firm). It also qualifies the policy debate: unification through an exact standard requires the stricter regulator to give up its power to exceed the common standard.

Formalizing it. The proofs in Online Appendix C are short computations in which several steps are "straightforward" or "easy to show". In particular, the existence and use of xˉ\bar xxˉ, the comparison between strategies at the regime boundaries, and the truncated branch of Proposition 2 are argued only briefly. A machine-checked development fixes the equilibrium notion, including how ties between strategies are treated, and verifies every inequality. To our knowledge none of these results has been formalized before.

Difficulty

The algebra of each step is elementary, but the base equilibrium is a bilevel object. R1R_1R1​ optimizes over s1s_1s1​ against a firm response that switches between three regimes at τU\tau_UτU​ and τS\tau_SτS​, and R1R_1R1​'s utility is a different concave quadratic in each regime. Showing that the split outcome sits at s1D∗s^*_{1D}s1D∗​ requires comparing the maximum over the DDD regime with the maxima over the UUU and SSS regimes. Only the third term of condition (1), through the implicitly defined xˉ\bar xxˉ, controls the UUU comparison. Simply substituting the closed forms of Lemma A.1 into the negotiation does not prove the goal: the goal quantifies over every split-market base outcome, so the characterization of the base equilibrium must actually be established. The emissions comparison also needs a strict inequality. At se∗=s1D∗s^*_e = s^*_{1D}se∗​=s1D∗​ the emissions in M1M_1M1​ are equal and only M2M_2M2​ changes, and the case se∗=0s^*_e = 0se∗​=0 must be excluded using condition (1).

Formalization scope

All quantities are real numbers in one parameter record (c,γ,h1,m1,m2,uˉ,b,r)(c, \gamma, h_1, m_1, m_2, \bar u, b, r)(c,γ,h1​,m1​,m2​,uˉ,b,r), and every statement assumes the standing assumptions of §3: c>0c > 0c>0, r>0r > 0r>0, h1≥(c−γ)/2h_1 \ge (c-\gamma)/2h1​≥(c−γ)/2, and uˉ≥max⁡{4r(m1+m2)/(m1m2), b(c−γ)}\bar u \ge \max\{4r(m_1+m_2)/(m_1 m_2),\ b(c-\gamma)\}uˉ≥max{4r(m1​+m2​)/(m1​m2​), b(c−γ)}. The formalization departs from or adds to the page in these places:

  • the page's c≥γc \ge \gammac≥γ is strengthened to c>γc > \gammac>γ, because every threshold divides by c−γc - \gammac−γ;
  • m1,m2>0m_1, m_2 > 0m1​,m2​>0 and b≥0b \ge 0b≥0 are made explicit;
  • γ\gammaγ's sign is left free;
  • s2=0s_2 = 0s2​=0 is fixed, as on p. 11;
  • the buying share is clipped to [0,1][0,1][0,1] and the margin uˉ−(c−γ)e\bar u - (c-\gamma)euˉ−(c−γ)e at 000. On [0,uˉ/(c−γ)][0, \bar u/(c-\gamma)][0,uˉ/(c−γ)] every quantity equals the page's formula, and above it a negative margin cannot square into a positive profit;
  • profits, sales and consumer utilities are the closed forms at p∗p^*p∗;
  • the firm's best response is not tie-broken, and a base-model outcome must beat R1R_1R1​'s utility at every alternative standard paired with every best response there. This makes the equilibrium value independent of tie-breaking;
  • xˉ\bar xxˉ enters as the greatest element of the root set of π1D(s1D∗)=π1U((uˉ−x)/(c−γ))\pi_{1D}(s^*_{1D}) = \pi_{1U}((\bar u - x)/(c-\gamma))π1D​(s1D∗​)=π1U​((uˉ−x)/(c−γ)), and a milestone shows that this greatest element exists;
  • under condition (1) with equalities, a unified outcome can tie with the split outcome for R1R_1R1​, so Lemma A.1(1) is stated as "(s1D∗,D)(s^*_{1D}, D)(s1D∗​,D) is an outcome, and every split outcome has s1=s1D∗s_1 = s^*_{1D}s1​=s1D∗​", not as uniqueness of the outcome;
  • the page's positivity argument for the gain fails when 2h1[uˉ+b(c−γ)]=(c−γ)uˉ2h_1[\bar u + b(c-\gamma)] = (c-\gamma)\bar u2h1​[uˉ+b(c−γ)]=(c−γ)uˉ, so positivity is stated under condition (1), which excludes that case.

A trivializing formalization is ruled out: the goal does not take the disagreement point from Lemma A.1's closed form or compare two formulas. It reads the disagreement point off an arbitrary split-market base outcome, asserts that one exists, and characterizes the negotiated standard through the Nash-product maximization. A sorry-free verification file checks that the goal's hypotheses hold together at a concrete parameter point (c=1c = 1c=1, γ=1/2\gamma = 1/2γ=1/2, h1=1h_1 = 1h1​=1, m1=m2=1/2m_1 = m_2 = 1/2m1​=m2​=1/2, uˉ=1000\bar u = 1000uˉ=1000, b=100b = 100b=100, r=20r = 20r=20).

The development needs only real algebra: quadratics, square roots and case analysis over three strategies. The lemmas on piecewise-quadratic best responses, and on the reduction of a transferable-utility Nash bargaining problem to total-utility maximization, may be reused for other regulator–firm models. Proofs of any milestone are welcome. Propositions 4 and 5 (baseline global standard, vertical negotiation) and the unified half of Proposition 2 are outside this mission.

Selected references

  • Z. Han, B. Hu, M. Dawande, Curbing Emissions: Environmental Regulations and Product Offerings Across Markets, Manufacturing & Service Operations Management, 2022. https://doi.org/10.1287/msom.2022.1141
  • J. F. Nash, The Bargaining Problem, Econometrica 18(2), 155–162, 1950. https://doi.org/10.2307/1907266
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EconomicsOperations Research·Captain: mikedeng1

Plumbing of Securities Markets: The Impact of Post-trade Fees on Trading and Welfare: Neither Uniform nor Trade-Specific Post-Trade Fees Maximize Welfare at Every Post-Trade CostResearch Paper

Why post-trade fees matter

Securities traders commonly pay for clearing and settlement after a trade is executed. A fee that is the same for every transaction is simple to administer, but processing a transaction between customers of the same broker can cost less than processing one between brokers. Degryse, Van Achter, and Wuyts ask whether charging everyone the same fee, or charging each transaction its processing cost, leads traders to make the trades that create the most total value. Their answer depends on the processing cost and on how traders' choice of limit-order quotes changes the next trader's choice. The October 2016 working paper develops this question in a single-security limit-order market; this mission uses its preprint page and result numbering.

Market and fee setting

In each period, one risk-neutral trader arrives. She is a buyer with probability 1/21/21/2 and values the security at VhV_hVh​, or a seller with probability 1/21/21/2 and values it at VlV_lVl​, where Vh>Vl≥0V_h>V_l\ge0Vh​>Vl​≥0. Each trader belongs to one of N>1N>1N>1 brokers, with equal arrival shares. A limit order offers one unit at a quoted bid or ask. It remains available for one period, so only the next trader can accept it. A market order accepts the standing quote immediately. The next trader may instead post her own limit order. Broker affiliations are visible, so a trader can choose a quote that attracts counterparties at every broker, called the all strategy, or only counterparties at her own broker, called the own strategy. The market description and tie rules appear in §3 of the working paper, pp. 8–9.

A trade within one broker is internalized; its processing cost is normalized to zero. A trade across brokers costs the post-trade service provider c>0c>0c>0 per leg. The uniform fee structure charges (N−1)c/N(N-1)c/N(N−1)c/N on each leg of every trade, while the trade-specific structure charges zero on an internalized leg and ccc on a cross-broker leg. These are the fee schedules analyzed in §4, pp. 10–13. They alter the gains from accepting a standing quote, and therefore the quotes that traders choose to post. A trader indifferent between a market order and a new limit order chooses the market order; a limit-order trader indifferent between attracting all brokers and only her own chooses all brokers.

The model tracks three possible actions in an order-flow chain: posting a limit order, executing an internalized market order, and executing a non-internalized market order. A stationary distribution φ=(φ0,φ1,φ2)\varphi=(\varphi_0,\varphi_1,\varphi_2)φ=(φ0​,φ1​,φ2​) gives their long-run frequencies. A trade's price transfers value between buyer and seller, while processing uses real resources. Thus expected welfare per period is

W(φ)=φ1(Vh−Vl)+φ2(Vh−Vl−2c).W(\varphi)=\varphi_1(V_h-V_l)+\varphi_2(V_h-V_l-2c).W(φ)=φ1​(Vh​−Vl​)+φ2​(Vh​−Vl​−2c).

This is the stationary-distribution form of Equation (6) in §5 and the Appendix, pp. 14–15 and Appendix pp. 1–2. It also gives welfare zero if no trade occurs.

Formalization targets

The goal is Corollary 3 of the working paper, p. 16. Two cost thresholds divide the outcomes:

c1=2N(N−1)(Vh−Vl)(2N+1)(2N−1),c2=N(Vh−Vl)2N+1.c_1=\frac{2N(N-1)(V_h-V_l)}{(2N+1)(2N-1)},\qquad c_2=\frac{N(V_h-V_l)}{2N+1}.c1​=(2N+1)(2N−1)2N(N−1)(Vh​−Vl​)​,c2​=2N+1N(Vh​−Vl​)​.

For c≤c1c\le c_1c≤c1​, the all strategy gives strictly higher welfare than own, and both fee structures induce all. For c1<c≤c2c_1<c\le c_2c1​<c≤c2​, all gives at least as much welfare; uniform fees induce all, while trade-specific fees induce own. For c>c2c>c_2c>c2​, own gives strictly higher welfare; trade-specific fees induce own and realize higher welfare than uniform fees. At c=c2c=c_2c=c2​, all and own have equal welfare. The two fee structures still induce different strategies there. The paper says that only uniform fees achieve the maximum in its middle range; at the equality endpoint, both welfare values attain the same maximum, so the formal statement preserves the equality and the distinct strategy choices.

Seven milestones support this target, in the paper's order. Equation (1) is the indifference system that optimal limit-order quotes satisfy. Proposition 1 classifies the equilibrium strategy under uniform fees, Equation (5) locates the cost c1c_1c1​ at which the limit-order profits of all and own coincide under trade-specific fees, and Proposition 2 classifies the trade-specific equilibrium. Appendix Equation (A3) gives the stationary distributions of the two order-flow chains, Equation (7) their trading rates, internalization rates and welfare, and Equation (8) the cost at which the two welfare levels agree. The proposition milestones also identify the resulting quotes and spreads; the welfare goal retains the paper's comparison of actual equilibrium outcomes.

What the result establishes

The distinction between the privately chosen strategy and the socially preferred one is operational: trade-specific fees can steer traders toward broker-only trading before that is best for total welfare, while uniform fees can leave them targeting every broker after broker-only trading becomes preferable. The theorem identifies the exact cost ranges in which each mismatch occurs. Its thresholds depend on the number of brokers and the spread in buyer and seller valuations. These claims, including the fact that neither fee schedule is best for the whole cost range, are stated in Corollary 3 and the discussion following it, pp. 16–17.

The result is proved in the paper. The remaining task here is to formalize its equilibrium classification and stationary welfare comparison in Lean, then give the published mathematical statements machine-checked proofs. The mission reuses a published finite-chain stationary-distribution definition; its three-state welfare accounting can serve related trading models, while the exact fee schedules and quote formulas belong to this paper's setting.

Main mathematical difficulty

The equilibrium cannot be found by comparing the welfare formulas alone: traders maximize their own expected limit-order profits. Whether a quote is accepted changes discretely when it crosses a counterparty's market-order threshold, and the value of posting the counterparty's new limit order is itself an equilibrium value. A quote attractive to all brokers and a quote attractive only to the same broker may each be optimal in different cost ranges. The analysis must also respect the paper's tie rules at both switching thresholds. Once the strategies are classified, the two three-state chains have different stationary trading frequencies, so a fee comparison at a fixed trade volume would not answer the question.

Formalization scope

Lean represents NNN as a natural number with 1<N1<N1<N and all money amounts as real numbers. The standing assumptions are 0≤Vl<Vh0\le V_l<V_h0≤Vl​<Vh​ and c>0c>0c>0; the latter expresses that the zero internalized cost is lower than the non-internalized cost. Division in threshold and quote formulas uses the real cast of NNN. A market order is chosen at equality, and an optimal all-broker quote is preferred at an all-versus-own tie. An equilibrium is a stationary pair of buyer and seller continuation values, each an attained greatest expected limit-order profit given the other. Optimal quotes determine the strategy; strategy labels are not defined by the cost thresholds.

The transition matrix has state indices 0,1,20,1,20,1,2 for limit, internalized market, and non-internalized market orders. A stationary distribution uses the published finite-chain definition: it is nonnegative, sums to one, and is a fixed row vector of that matrix. The printed third row of Appendix (A2) is all zeros even though the text calls the matrix stochastic. The formal matrix sends that unreachable state back to state 000; this changes no stationary probability in (A3). Welfare is calculated from the stationary distribution and true processing costs, not assigned one of the closed formulas in Equation (7). The goal quantifies over equilibrium continuation values and stationary distributions, while the milestones assert their existence and identify the distributions. Contributions that establish these equilibrium, finite-chain, and threshold results are within scope.

Selected references

  • Hans Degryse, Michael Van Achter, and Gunther Wuyts, Plumbing of Securities Markets: The Impact of Post-Trade Fees on Trading and Welfare, SSRN working paper 2023597, October 2016. SSRN.
  • Hans Degryse, Michael Van Achter, and Gunther Wuyts, Plumbing of Securities Markets: The Impact of Post-Trade Fees on Trading and Welfare, Management Science, 2021. DOI. The source used for formalization is the October 2016 working paper.
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EconomicsOperations Research·Captain: mikedeng1

A Theory of Assurance: Balancing Costly Formal Control with Tone at the Top: The Authority's Optimal Formal Control and the High-Type CEO's Tipping Point in the Diversion ModelResearch Paper

Motivation

Boards and audit committees use formal controls to limit the resources that an executive can divert. Controls can also change the executive's decision: a CEO who values her future reputation may comply when the remaining opportunity to divert is too small. Penno's diversion model puts these two effects in one decision problem. It asks how much costly control the authority should buy when it does not know in advance which CEO type it will draw. The answer depends on the chance of drawing a reputation-sensitive CEO and on the strength of that CEO's career concerns. Penno calls their product tone at the top.

The source for this mission is the May 2019 revision of Penno's SSRN working paper. Its Proposition 1 gives an explicit optimal control level and the corresponding temptation threshold for the high CEO type. The result belongs to a theoretical accounting model; the mission concerns that model's mathematical assertion, rather than an estimate of actual control costs or misconduct.

Setting

An authority chooses a formal control level ccc before a CEO sees a temptation xxx. The temptation is uniform on [0,xˉ][0,\bar x][0,xˉ], where xˉ>0\bar x>0xˉ>0. If the CEO diverts resources, the authority loses (1−c)x(1-c)x(1−c)x; if the CEO complies, it loses none to diversion. The authority also pays the direct cost K(c)=λ/(1−c)K(c)=\lambda/(1-c)K(c)=λ/(1−c), with λ>0\lambda>0λ>0. The control domain is 0≤c<10\le c<10≤c<1: full control has infinite cost in the paper.

A CEO has type η∈{0,ηH}\eta\in\{0,\eta_H\}η∈{0,ηH​}, with ηH>0\eta_H>0ηH​>0. The high type is drawn with probability p∈(0,1)p\in(0,1)p∈(0,1) and the low type with probability 1−p1-p1−p. For a CEO of type η\etaη, diversion gives utility βη+γ(1−c)x\beta\eta+\gamma(1-c)xβη+γ(1−c)x and compliance gives utility η\etaη, where β<1\beta<1β<1 and 0<γ<10<\gamma<10<γ<1. Define τ=(1−β)ηH/γ\tau=(1-\beta)\eta_H/\gammaτ=(1−β)ηH​/γ. The high type diverts when xxx exceeds her tipping point xT(c)=τ/(1−c)x_T(c)=\tau/(1-c)xT​(c)=τ/(1−c); the low type diverts for any positive temptation. The paper assumes τ<xˉ\tau<\bar xτ<xˉ so that the high type can divert under some control levels.

Write L(c)L(c)L(c) for the authority's expected loss: the expected amount diverted, averaged over both CEO types and the uniform temptation, plus K(c)K(c)K(c). When c<1−τ/xˉc<1-\tau/\bar xc<1−τ/xˉ, both types can divert. At and above that boundary the high type never diverts, so only the low type contributes to expected diversion. The definition of LLL in this mission starts from the CEO's utility comparison and integrates the resulting diverted amount. This preserves the decision mechanism underlying the two closed forms in the paper's appendix.

Formalization targets

Proposition 1: optimal control and tipping point

Under the standing model assumptions and the two conditions of Lemma 1, let q=2λxˉ/(1+p)q=\sqrt{2\lambda\bar x/(1+p)}q=2λxˉ/(1+p)​. Proposition 1 states that the unique optimal control and its high-type tipping point are

c∗={1−2λxˉ−pτ2xˉ,τ≤q,1−τxˉ,τ≥q,xT(c∗)={τxˉ2λxˉ−pτ2,τ≤q,xˉ,τ≥q.c^*=\begin{cases} 1-\dfrac{\sqrt{2\lambda\bar x-p\tau^2}}{\bar x},&\tau\le q,\\[4pt] 1-\dfrac{\tau}{\bar x},&\tau\ge q, \end{cases} \qquad x_T(c^*)=\begin{cases} \dfrac{\tau\bar x}{\sqrt{2\lambda\bar x-p\tau^2}},&\tau\le q,\\[4pt] \bar x,&\tau\ge q. \end{cases}c∗=⎩⎨⎧​1−xˉ2λxˉ−pτ2​​,1−xˉτ​,​τ≤q,τ≥q,​xT​(c∗)=⎩⎨⎧​2λxˉ−pτ2​τxˉ​,xˉ,​τ≤q,τ≥q.​

Both branches include equality at qqq; their values agree there. The formal goal states that the displayed control belongs to [0,1)[0,1)[0,1) and has strictly less expected loss than every other admissible control. The paper's printed formula can be negative for sufficiently large λ\lambdaλ, even when Lemma 1 holds. The goal therefore adds the necessary condition 2λxˉ−pτ2≤xˉ22\lambda\bar x-p\tau^2\le\bar x^22λxˉ−pτ2≤xˉ2, which ensures that the first branch remains an admissible control.

The milestone list follows the model's tipping point (5), the two expected-loss formulas, the convexity and increasing-loss assertions of Lemma 1, and the appendix's first-order and branch-threshold equations. These are source claims used to identify the optimizer, with their original indices and page provenance.

Significance

The result describes when stronger reputational incentives accompany more formal control and when they allow the authority to reduce it. The threshold qqq separates an interior solution, where the high type can still divert at sufficiently large temptations, from a boundary solution that keeps the high type compliant throughout the support of xxx. The accompanying expression for xTx_TxT​ makes the behavioral meaning of each branch explicit. Penno uses the result to discuss the relation between tone at the top and formal control in the basic diversion model.

The paper supplies an analytic proof. This mission seeks machine-checked proofs of the same optimization claim and of its supporting statements. Its definition of expected loss also provides a small reusable example of a two-type decision model with a choice-dependent threshold inside an integral. The mathematical result is known from the paper; its Lean proof remains the work of the mission.

Difficulty

A direct optimization of λ/(1−c)\lambda/(1-c)λ/(1−c) alone misses the expected diversion term, while treating the high type as always compliant misses the change of behavior at xT(c)x_T(c)xT​(c). The loss is piecewise because the high type's tipping point can move past the upper end of the temptation interval. A complete argument must establish the two losses from the utility-based diversion rule, control their behavior on the correct intervals, and compare the candidate in the first interval with their shared boundary. The value c=1c=1c=1 also needs separate attention: ordinary real division assigns λ/0\lambda/0λ/0 a value, whereas the paper assigns infinite cost to full control.

Formalization scope

Lean uses real parameters xˉ,λ,p,β,γ,ηH\bar x,\lambda,p,\beta,\gamma,\eta_Hxˉ,λ,p,β,γ,ηH​ bundled in Params, together with the standing inequalities of §3. It represents uniform temptation by an interval integral of the diverted amount with density 1/xˉ1/\bar x1/xˉ. The CEO diverts exactly when her diversion utility is strictly greater than her compliance utility. At equality, the formal model takes compliance; that single threshold point has no effect on the integral. The high type's tipping point is the unconstrained value τ/(1−c)\tau/(1-c)τ/(1−c), which can exceed xˉ\bar xxˉ even though realized temptations cannot.

All optimization statements use c∈[0,1)c\in[0,1)c∈[0,1). This agrees with the source convention K(1)=∞K(1)=\inftyK(1)=∞ and avoids treating Lean's real division by zero as a finite control cost. The added inequality 2λxˉ−pτ2≤xˉ22\lambda\bar x-p\tau^2\le\bar x^22λxˉ−pτ2≤xˉ2 is disclosed in the goal and is needed only to keep the printed interior formula nonnegative. There is no assumption that β\betaβ is nonnegative: the source only requires β<1\beta<1β<1. The first part of Lemma 1 is strict convexity; its second part is expressed as strict increase, as stated in the appendix proof.

The development needs Mathlib's interval integrals, real square root, and real convexity and monotonicity predicates. Contributions that establish the integral closed forms, the behavior of the two loss regions, and the global optimality claim are within scope. A definition that merely hard-codes the appendix's closed forms as LLL, or a goal about an unconstrained control, would lose the CEO choice and the authority's actual feasible set.

Selected references

  • M. Penno, A Theory of Assurance: Balancing Costly Formal Control with Tone at the Top, SSRN working paper 2876700, revision of May 2019, §§3–4 and Appendix, pp. 6–13, 28–29. SSRN
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EconomicsMechanism Design·Captain: mikedeng1

Voting with Time Commitment for Decentralized Governance: Bond Voting as a Sybil-Resistant Mechanism: Bond Voting Is Robustly v-ImplementableResearch Paper

Motivation

Blockchain platforms and decentralized autonomous organizations take governance decisions by token-weighted voting: an account's influence grows with the governance tokens it stakes. Two problems are associated with this design (Buterin 2021). The first is plutocracy: holders of many tokens control decisions. The second is the Sybil attack (Douceur 2002): accounts are pseudonymous, so one person can split her tokens over many identities. A rule that dampens the influence of large stakes — for example votes proportional to the square root of tokens — invites exactly this splitting, because the dampening is undone by holding many small stakes.

Mohan, Khezr and Berg (SSRN 4259599; Management Science 2024, doi:10.1287/mnsc.2023.01536) set up a model in which votes depend on two resources, staked tokens and time commitment. They characterize Sybil resistance (Theorem 1), show that token weighting alone cannot be both plutocracy- and Sybil-resistant (Theorem 2, the Plutocracy–Sybil dilemma), and propose bond voting, in which votes are bought with voting bonds that lock tokens until maturity. This mission formalizes the paper's main positive result: bond voting is robustly v-implementable (Proposition 2).

Setting

A platform fixes a maximal commitment horizon T>0T > 0T>0. A vote function v(q,t)v(q, t)v(q,t) turns a stake of q≥0q \ge 0q≥0 tokens locked for t∈[0,T]t \in [0, T]t∈[0,T] units of time into votes, with v(q,0)=v(0,t)=0v(q, 0) = v(0, t) = 0v(q,0)=v(0,t)=0 (Definition 1). It values commitment if ∂v/∂t>0\partial v/\partial t > 0∂v/∂t>0, and has non-increasing influence of tokens if ∂v/∂q>0\partial v/\partial q > 0∂v/∂q>0 and ∂2v/∂q2≤0\partial^2 v/\partial q^2 \le 0∂2v/∂q2≤0, for all q>0q > 0q>0 and t∈(0,T]t \in (0, T]t∈(0,T] (Definitions 2, 3).

An agent with budget q>0q > 0q>0 and payoff function π(q,t)\pi(q, t)π(q,t) chooses t∈[0,T]t \in [0, T]t∈[0,T]. A Sybil attack with MMM identities assigns stakes q1,…,qM≥0q_1, \dots, q_M \ge 0q1​,…,qM​≥0 and commitments t1,…,tMt_1, \dots, t_Mt1​,…,tM​. It is feasible if ∑mqm≤q\sum_m q_m \le q∑m​qm​≤q and every tm∈(0,T]t_m \in (0, T]tm​∈(0,T], and profitable if its payoff ∑mπ(qm,tm)\sum_m \pi(q_m, t_m)∑m​π(qm​,tm​) strictly exceeds what the agent obtains as a single entity (Definition 5). A payoff function is Sybil resistant if no budget admits a feasible and profitable attack (Definition 6), and a mechanism is robustly v-implementable if its vote function values commitment, has non-increasing influence of tokens, and is Sybil resistant (Definition 7).

Bond voting. The platform sets a voting bond rate rrr. A ttt-bond costs Pt=e−rtP_t = e^{-rt}Pt​=e−rt tokens, returns them at maturity, and carries one vote, so a budget qqq buys V=q/Pt=qertV = q/P_t = q e^{rt}V=q/Pt​=qert votes. An agent of type (θ,u,ri)(\theta, u, r_i)(θ,u,ri​) — marginal pivotality θ\thetaθ, value uuu of the policy, outside return rir_iri​ on her tokens — receives benefit ∣u∣θV|u|\theta V∣u∣θV and bears the opportunity cost q(erit−1)q(e^{r_i t} - 1)q(eri​t−1), so for t>0t > 0t>0

πi(q,t)=∣u∣θ q ert−q (erit−1),πi(q,0)=0.\pi_i(q, t) = |u|\theta\, q\, e^{rt} - q\,(e^{r_i t} - 1), \qquad \pi_i(q, 0) = 0.πi​(q,t)=∣u∣θqert−q(eri​t−1),πi​(q,0)=0.

Agent types are admissible when ∣u∣θ>1|u|\theta > 1∣u∣θ>1 and ri>rr_i > rri​>r.

Formalization targets

Goal: Proposition 2

For every rate r>0r > 0r>0 and horizon T>0T > 0T>0,

bond voting  =  (v(q,t)=qert, {πi:(θ,u,ri) admissible}) is robustly v-implementable.\text{bond voting} \;=\; \Bigl(v(q,t) = q e^{rt},\ \{\pi_i : (\theta, u, r_i)\ \text{admissible}\}\Bigr)\ \text{is robustly v-implementable.}bond voting=(v(q,t)=qert, {πi​:(θ,u,ri​) admissible}) is robustly v-implementable.

The goal quantifies over every admissible agent type and every budget, and leaves rrr and TTT free.

Milestones

  1. Equation (5): the closed form of πi\pi_iπi​ above.
  2. The bond vote function satisfies Definitions 2 and 3.
  3. Proposition 1, cases 1–2: if ri<θ∣u∣rr_i < \theta|u| rri​<θ∣u∣r, the optimal bond length is ti∗=Tt^*_i = Tti∗​=T when ri≤θ∣u∣r e−T(ri−r)r_i \le \theta|u| r\, e^{-T(r_i - r)}ri​≤θ∣u∣re−T(ri​−r), and ti∗=ln⁡(θ∣u∣r/ri)/(ri−r)t^*_i = \ln(\theta|u| r/r_i)/(r_i - r)ti∗​=ln(θ∣u∣r/ri​)/(ri​−r) otherwise; it is the unique maximizer of πi(q,⋅)\pi_i(q, \cdot)πi​(q,⋅) on [0,T][0, T][0,T] and does not depend on qqq.
  4. Theorem 1, "if" direction: a payoff linear in qqq for every t∈(0,T]t \in (0, T]t∈(0,T], vanishing at q=0q = 0q=0 and at t=0t = 0t=0, is Sybil resistant.
  5. The Sybil step of the proof of Proposition 2: under the hypotheses of milestone 3, no feasible attack earns more than πi(q,ti∗)\pi_i(q, t^*_i)πi​(q,ti∗​).

Significance

The result. Proposition 2 shows that a second voting resource, time, can be added to token voting without reopening the Sybil problem: bond votes are linear in tokens, so splitting across identities earns nothing, while voters with a low opportunity cost of locking tokens, or a strong stake in the outcome, gain influence through longer commitments. Together with Theorem 2, which shows that token weighting alone cannot dampen large holdings without inviting Sybil attacks, it is the paper's case for bond voting as a governance mechanism.

Formalizing it. The result is proved on paper; it has no machine-checked proof. Formalization adds two things beyond a check. First, it fixes the definitions the paper leaves implicit: the payoff of a multi-identity attack, and which single-entity commitment a profitable attack must beat. Second, it states Proposition 1 precisely: the printed third case of equation (6) (ti∗=0t^*_i = 0ti∗​=0 when ri≥θ∣u∣rr_i \ge \theta|u| rri​≥θ∣u∣r) has no maximizer, because the payoff tends to θ∣u∣q>0\theta|u| q > 0θ∣u∣q>0 as t→0+t \to 0^+t→0+ but is 000 at t=0t = 0t=0. The goal is stated so that it remains true for those agent types.

Difficulty

The mathematics is elementary real analysis; the difficulty is in the definitions. The naive reading of Definition 5(c) compares an attack with the agent's payoff at a fixed commitment tit_iti​. Under that reading the "if" half of Theorem 1 fails: an agent with a suboptimal tit_iti​ gains by moving her whole budget to one identity with a better commitment. Comparing with the formula ti∗t^*_iti∗​ instead fails in the third case of (6). The statement holds when the attack must beat every commitment the agent could choose herself, and proving it then requires handling agent types with no optimal commitment, where Proposition 1 cannot be invoked. Discontinuity of πi\pi_iπi​ at t=0t = 0t=0 also rules out arguments that take a maximum over the compact interval [0,T][0, T][0,T].

Formalization scope

Everything is real-valued (ℝ), with Real.exp and Real.log. Identities are indexed by Fin M; M=0M = 0M=0 (no identities) and identities with zero stake are allowed. Derivatives in Definitions 2–3 are encoded with HasDerivAt witnesses, not with deriv, so a non-differentiable function cannot satisfy them by default values. The payoff of an attack is the sum of the identities' payoffs, as computed in the paper's proofs (pp. 16, 25). An attack is profitable only if it beats every single-entity commitment t∈[0,T]t \in [0, T]t∈[0,T], including t=0t = 0t=0 (not voting). Bond votes and payoffs are 000 at t=0t = 0t=0, as the paper imposes. The hypothesis r>0r > 0r>0 is added: the paper never states the sign of rrr, and Definition 2 fails without it.

Fixing the single entity's commitment to ti∗t^*_iti∗​, or proving Sybil resistance only for agent types covered by Proposition 1 cases 1–2, would be a trivializing formalization of the goal; the goal quantifies over all admissible types and all single-entity commitments.

Theorem 1 is stated "given Assumptions 1 and 2" for mechanisms with non-increasing influence of tokens; milestone 4 drops these hypotheses because its proof uses only linearity and the boundary conditions. Not formalized: Theorem 1's "only if" direction (its proof uses a fixed single-entity commitment and equates nonlinearity with strict concavity), Theorem 2 and Corollaries 1–4, Remarks 1–4, Proposition 3, and the numerical sensitivity analysis of §3.3. All definitions live in one file in the namespace BondVoting.Sybil; the attack and resistance definitions are stated for an arbitrary payoff function and can be reused for other voting rules, such as quadratic voting.

Selected references

  • V. Mohan, P. Khezr, C. Berg, Voting with time commitment for decentralized governance: Bond voting as a Sybil-resistant mechanism, SSRN 4259599 (version of 2024-02-20); Management Science, 2024. https://ssrn.com/abstract=4259599, https://doi.org/10.1287/mnsc.2023.01536
  • J. R. Douceur, The Sybil attack, International Workshop on Peer-to-Peer Systems (IPTPS), LNCS 2429, 2002. https://doi.org/10.1007/3-540-45748-8_24
  • V. Buterin, Moving beyond coin voting governance, 2021. https://vitalik.ca/general/2021/08/16/voting3.html
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Motives·Captain: Lucas

Motives — Grothendieck's dream: effective pure motives and the tannakian obstructionResearch Paper

Mission: Motives — effective pure motives and the tannakian obstruction

Motivation

Grothendieck introduced the notion of a motive in a letter to Serre in 1964. Among all the objects he was privileged to discover, he wrote, this one appeared to him the most charged with mystery, and the yoga of motives perhaps the most powerful instrument of discovery he had brought to light. The source — James Milne's expository article "Motives — Grothendieck's Dream" — explains what motives are and why Grothendieck valued them so highly. The many good cohomology theories of algebraic geometry — singular, étale, de Rham, crystalline — cannot come from an algebraically defined Q-valued theory, yet they behave as though they did: traces of regular maps are rational and independent of the theory. Grothendieck's answer is a universal cohomology theory with values in a Q-linear category of motives: every good cohomology theory should factor uniquely through it. The construction passes through algebraic cycles modulo an adequate equivalence relation and correspondences; the category so obtained is additive and pseudo-abelian, carries a tensor product satisfying the Künneth formula, and its first computed decomposition is the motive of the projective line, h(P¹) = 𝟙 ⊕ 𝕃, whose endomorphism ring is as small as possible; the trace of the identity on a motive is the Euler-Poincaré characteristic, and the first zeta computations — the point and the projective line — exhibit the mechanism that the Weil conjectures later vindicated in general. The same trace calculus, however, contains the obstruction that Grothendieck's dream runs against: the trace of the identity on the motive of a curve of genus g is 2 − 2g, which is negative for g ≥ 2, so no fiber functor can exist on the category of effective motives and the category cannot be tannakian.

The mission formalizes the definitions and the proved structural theorems of Sections 4-7 of the source: the algebra of correspondences, the category of effective pure motives with its composition, addition, tensor structure, and pseudo-abelian splitting, Grothendieck's decomposition of the motive of the projective line, the trace of the identity as the Euler characteristic, the zeta functions of a point and of the projective line, and — as the goal — the tannakian obstruction: the category of effective motives admits no fiber functor in the presence of a curve of genus at least 2.

The fragment and its conventions

The source is an expository article; the mission formalizes the fragment consisting of the correspondence algebra and the category of effective pure motives (Sections 4-6), the trace calculus (Section 6, page 10), and the first two zeta computations (Section 7), under the following disclosed conventions.

Fourteen conventions deserve disclosure. First, the platform publishes definitions as modules, so the three definition bundles — the correspondence world, the effective motives, and the zeta coefficients — are published as platform definitions (Milne_world, Milne_motives, Milne_zeta) and 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, algebraic geometry is abstract: no varieties, algebraic cycles, Chow groups, or cohomology theories are constructed, since Mathlib has none of this; the primitive datum is a world of correspondences (CorrWorld) — varieties with a product, a designated point, a projective line, and a curve of every genus, and for each pair of varieties a Q-vector space of correspondences carrying a degree function into the integers, composition, diagonals, transposes, exterior products, Künneth idempotents, and trace data — with the moving lemmas and the well-definedness of the products of cycle classes living in the interface fields, so that every theorem carries the world as a hypothesis. Third, correspondences are presented ungraded, with the grading recovered through the degree function: the graded pieces Corr^r(X, Y) are the degree-r elements, and morphisms of motives are the degree-zero correspondences of the source's f ∘ Corr⁰(X, Y)Q ∘ e. Fourth, rational coefficients are baked into the interface: the correspondence spaces are Q-vector spaces, the source's tensoring of cycle groups with Q is not repeated. Fifth, the mission lives in the effective category: the paper's second attempt of Section 5; the twist integer m of h(X, e, m), duals, and the full category M~(k) are out of scope. Sixth, morphisms are rendered as fixed points: the sandwiched image f ∘ Corr(X, Y)_Q ∘ e is the subtype of correspondences γ with f ∘ γ ∘ e = γ and degree zero, which coincides with the image when e and f are idempotent. Seventh, the closure of the sandwiched subspaces under the operations (composition, addition, zero, negation, scalar multiplication, exterior product) is imposed through interface axioms, since these are the stability statements that make the morphism spaces well defined. Eighth, direct sums are stated through the five biproduct identities rather than as an equality with a direct-sum object; the pseudo-abelian splitting is stated through the same identities, with the complement and image summands h(X, e − f) and h(X, f) as the explicit witnesses. Ninth, the tensor structure is defined on objects and morphisms through the exterior product, and the Künneth formula is stated at the level of motives: hX ⊗ hY = h(X × Y). Tenth, the Künneth idempotents of the projective line and of the curves of every genus, the diagonal decompositions Δ = e₀ + e₂ and Δ = π₀ + π₁ + π₂, and the trace values 1, −2g, 1 of the pieces — the signed Betti numbers, so that the trace of the identity is the Euler characteristic — are interface data: the source's computations from the intersection ring of the projective plane and of a curve are thereby carried as hypotheses. Eleventh, the trace of the identity on an idempotent motive is defined through the interface-supplied evaluation and coevaluation correspondences, its additivity over idempotent splits is an interface axiom, and the duality zigzag equations of the source are not stated. Twelfth, the fiber functor is rendered as a concrete structure FibFun — a dimension for each motive, an action on morphisms, preservation of identities and composition, multiplication of dimensions over tensor products, and the identification of the trace of the identity with the dimension of the fiber; exactness and faithfulness are deliberately not hypothesized, because the tannakian obstruction needs only the trace-dimension identity, so the goal theorem is formally stronger than the source's formulation — the strengthening is disclosed — and the fibers are Q-vector spaces, whereas the source allows any field F of characteristic zero. Thirteenth, the zeta function is rendered through its Taylor coefficients via a course-of-values prefix recursion equivalent to the source's logarithmic definition log Z(X, t) = Σ N_m t^m / m; the point counts 1 and 1 + p^m of the point and of the projective line are carried as data, and no finite fields are formalized. Fourteenth, everything is developed against the platform's Mathlib build (0df444a); 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.

Formalization targets

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

  • The correspondence world (reference): varieties with a product, a point, a projective line, curves of every genus, and Q-vector spaces of correspondences with composition, diagonals, transposes, exterior products, degrees, Künneth idempotents, and trace data (Sections 4-6).
  • Effective pure motives (reference): objects h(X, e), morphisms as sandwich-fixed degree-zero correspondences, identity, composition, addition, zero, tensor products, the summands of the projective line, the splitting summands, and the fiber functor structure (Sections 5-6).
  • Zeta functions (reference): the Taylor coefficients of the zeta function attached to a point-count sequence, through the prefix recursion (Section 7).
  • Effective motives form a category: associativity of composition and the identity laws (Section 5) — milestone.
  • Effective motives are pseudo-abelian: an idempotent endomorphism splits the motive into biproduct summands (Section 6) — milestone.
  • The tensor product and the Künneth formula: the interchange law, the tensor identity, and hX ⊗ hY = h(X × Y) (Section 6) — milestone.
  • The motive of the projective line: h(ℙ¹) = 𝟙 ⊕ 𝕃, and the endomorphism ring is the rational span of the two Künneth idempotents (Sections 5-6) — milestone.
  • The trace of the identity on the motive of a curve is its Euler characteristic 2 − 2g (Section 6, p. 10) — milestone.
  • The zeta function of a point: all Taylor coefficients are 1 (Section 7) — milestone.
  • The zeta function of the projective line: the Taylor coefficients are the partial geometric sums (Section 7) — milestone.
  • The tannakian obstruction: no fiber functor exists on the effective motives of a world containing a curve of genus at least 2 (Section 6, p. 10) — the goal.

Significance

The formalized fragment is the additive and tensor skeleton that every theory of motives shares, together with the trace calculus and the first two zeta computations, and it ends with the obstruction that gives the mission its point: as long as the trace of the identity on the motive of a curve is its Euler characteristic, no fiber functor can exist, so the category of effective motives is not tannakian and cannot be the representation category of an affine group scheme — the reason the source gives for passing to larger categories of motives. Formalizing the skeleton with every geometric input isolated as an explicit interface hypothesis produces a reusable shape: the same statements admit any future Mathlib development of algebraic cycles as an instantiation.

Difficulty

The categorical skeleton is pure algebra: associativity, units, biproduct identities, the interchange law, and the splitting of idempotents follow from the interface axioms by equational reasoning; the trace computation is additivity over the Künneth decomposition together with the supplied trace values; the zeta computations are inductions on the coefficient recurrence; the goal is the contradiction between a negative trace and the nonnegativity of a dimension. The difficulty is the discipline of the interface — no statement may silently use a geometric fact that has not been assumed — and the bookkeeping of the course-of-values recursion against the geometric expansion of the reciprocal of (1 − t)(1 − p t).

Formalization scope

Every item quantifies only over the objects it needs — worlds, motives, morphisms, idempotents, genera, point-count sequences. The goal carries a genus parameter together with the hypothesis that the genus is at least two; every world contains a curve of every genus by the interface, so the hypothesis is satisfiable, and it states the source of the obstruction — the middle Künneth summand of a curve of genus at least two has negative trace. This binder is disclosed here rather than left unstated. The negation-free statements produce witnesses: biproducts, splittings, and decompositions produce their morphisms; the zeta identities are equalities of coefficients; the goal is a negation, as is proper for an obstruction. The fragment excludes the twist m ∈ ℤ, duals, rigidity, and tannakianity as a positive property (Sections 5-6), the abelian category M_num and its semisimplicity, Conjectures C and D and the standard conjectures (Section 6), the zeta function of a motive via characteristic polynomials of Frobenius and the Hasse-Weil bound (Sections 2, 7-8), motivic L-functions, the big modularity conjecture, and the conjecture of Birch and Swinnerton-Dyer (Sections 8-9), and mixed motives (Section 10) — everything the source conjectures rather than proves, and everything requiring cohomological realization, is out of scope. The mission formalizes what the source proves.

Selected references

  • J. S. Milne, Motives — Grothendieck's Dream, v2.04, April 24, 2012 — the mission's source.
  • A. Grothendieck, letter to J.-P. Serre, 1964 — the introduction of the notion of motif.
  • S. L. Kleiman, Motives, in Algebraic Geometry, Oslo 1970 — the first detailed exposition of the standard conjectures.
  • U. Jannsen, S. L. Kleiman, J.-P. Serre (eds.), Motives, Proceedings of Symposia in Pure Mathematics 55, American Mathematical Society, 1994 — the standard reference, including Scholl's detailed construction of the category of motives.
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Number Theory·Captain: Lucas

The first Hardy-Littlewood conjecture: the asymptotic density of prime constellationsOpen Problem

Motivation

In 1923 Hardy and Littlewood proposed two conjectures about the distribution of primes that have shaped a century of analytic number theory. The first — the prime kkk-tuple conjecture — predicts that every admissible prime constellation (p,p+m1,…,p+mk)(p, p + m_1, \dots, p + m_k)(p,p+m1​,…,p+mk​) occurs with a precise asymptotic density: the number πP(n)\pi_P(n)πP​(n) of constellations with base point p≤np \le np≤n grows like CP∫2ndt/(log⁡t)k+1C_P \int_2^n dt/(\log t)^{k+1}CP​∫2n​dt/(logt)k+1, where the singular series constant CPC_PCP​ is an explicit Euler product over the residues of the offsets modulo the primes. For the twin offsets this specializes to the twin prime conjecture with the twin-prime constant 2C2≈1.32032C_2 \approx 1.32032C2​≈1.3203. The second conjecture asserts that the prime-counting function is subadditive: π(x+y)≤π(x)+π(y)\pi(x+y) \le \pi(x) + \pi(y)π(x+y)≤π(x)+π(y). Richards proved in 1974 that the two conjectures are incompatible — at most one of them is true. The source file states all three results in Lean 4: the two conjectures as open problems, and the incompatibility as a theorem.

The mission takes the first conjecture — the file's title statement, and the one widely believed — as its goal. It formalizes the conjecture's definitional core (prime constellations, admissibility, counting functions, the singular series), and curates as milestones the structural facts any proof must engage: the translation-invariance of admissibility, its necessity for primality, the vanishing count for inadmissible tuples, the divergence of the logarithmic-integral model, the positivity of the singular series, the infinitude consequences down to the twin prime conjecture, and Richards' incompatibility with the second conjecture.

Timeline

  • 1923 — G. H. Hardy and J. E. Littlewood state the prime kkk-tuple conjecture and the subadditivity conjecture for the prime-counting function in Some problems of "Partitio numerorum"; III, Acta Mathematica 44, pp. 1–70.
  • 1974 — Ian Richards proves that the two conjectures are incompatible: the first, asserted for all tuples, implies the failure of the second for some pair x,yx, yx,y.
  • 2025 — the Formal Conjectures project formalizes both conjectures and Richards' theorem in Lean 4; the present mission is built directly on that file (HardyLittlewood.lean).

The fragment and its conventions

The arena is the set of prime constellations: tuples (p,p+2m1,…,p+2mk)(p, p + 2m_1, \dots, p + 2m_k)(p,p+2m1​,…,p+2mk​) of primes with even gaps, encoded by a function m:{0,…,k}→Nm : \{0, \dots, k\} \to \mathbb{N}m:{0,…,k}→N of offsets with m0=0m_0 = 0m0​=0. A constellation is admissible when its entries do not form a complete set of residue classes modulo any prime; the counting function πP(n)\pi_P(n)πP​(n) counts admissible constellations with base point at most nnn; the singular series CPC_PCP​ is 2k∏q≥31−w(q;m)/q(1−1/q)k+12^k \prod_{q \ge 3} \frac{1 - w(q;m)/q}{(1 - 1/q)^{k+1}}2k∏q≥3​(1−1/q)k+11−w(q;m)/q​ with w(q;m)w(q; m)w(q;m) the number of residues occupied by the offsets modulo qqq; and the conjecture asserts πP(n)∼CP∫2ndt(log⁡t)k+1\pi_P(n) \sim C_P \int_2^n \frac{dt}{(\log t)^{k+1}}πP​(n)∼CP​∫2n​(logt)k+1dt​ for tuples with distinct offsets.

Nine conventions deserve disclosure. First, the platform publishes definitions as modules Definitions.Def_<definition_name>, so the three definition bundles — constellations and admissibility, counting functions, and the asymptotic layer with the singular series — are published as platform definitions (HardyLittlewood_constellation, HardyLittlewood_counting, HardyLittlewood_series) and attached to the proposal as reference items; the theorem drafts import them. Second, asymptotic equivalence is phrased through a self-contained definition — f ~ g when the difference is little-o of g — rather than an external asymptotic-equivalence notation; the formulation coincides with the classical ratio limit when the model sequence is eventually positive and unbounded, and it degenerates correctly: for an inadmissible tuple the singular series is zero, the model vanishes identically, and the conjecture asserts exactly that the counting function is eventually zero, which is the true degenerate content. Third, the counting functions are defined as the cardinalities of finite sets of natural numbers (noncomputable, Classical), with π\piπ counting primes up to and including nnn, matching the source's phrasing. Fourth, admissibility is split: the source's constellation-level condition is kept verbatim, and the parameter-free condition on the doubled offsets (IsAdmissibleTuple) is added beside it; the equivalence — residue coverage is invariant under translation by the base point — is the mission's first milestone, so nothing is assumed that is not proved. Fifth, the residue count w(q;m)w(q; m)w(q;m) is taken on the offsets themselves, exactly as the source's numResidues; at every odd prime this agrees with the count for the doubled offsets 2mi2m_i2mi​, and the product runs over the primes q≥3q \ge 3q≥3 with the source's normalization and 2k2^k2k prefactor. Sixth, the singular series constant is defined through the unconditional infinite product; its convergence and positivity are not assumed anywhere — they are the content of a milestone, and the hypothesis that makes the product converge (pairwise distinct offsets) is stated there explicitly, since a repeated offset forces every factor to be 1+O(1/q)1 + O(1/q)1+O(1/q) and the product to diverge. Seventh, a curation decision: the goal is the first conjecture; the second conjecture is deliberately not drafted as a provable item, because Richards' theorem — itself a milestone — shows that the two cannot both hold; the second conjecture appears as a definition and inside the incompatibility milestone. Eighth, the goal is stated for every tuple, with the conjecture's own hypotheses (m0=0m_0 = 0m0​=0 and pairwise distinct offsets) inside the predicate, exactly as the source file states it. Ninth, the read-backs attached to the drafts were written by the same model that produced the statements (readback_model glm-5-latest-short), not by an independent auditor; the human item-by-item comparison against the source remains the main defense against an unfaithful formalization.

Formalization targets

The goal is the first Hardy–Littlewood conjecture for every tuple. The supporting chain, in attack order, each step a milestone except the last:

  • Translation invariance: a prime constellation at p is admissible exactly when it is a prime constellation and the doubled offsets are admissible.
  • Necessity: if the residues of the entries cover all classes modulo a prime q < p, the tuple is not a prime constellation at p — some entry is a multiple of q larger than q.
  • Vanishing: an inadmissible tuple has an identically zero counting function.
  • Divergence: for every multiplicity, the model integral of 1/(log⁡t)k+11/(\log t)^{k+1}1/(logt)k+1 from 2 to n tends to infinity.
  • Positivity: for an admissible tuple of distinct offsets, the singular series constant is a strictly positive real.
  • Infinitude: the conjecture, for an admissible tuple of distinct offsets, yields prime constellations at arbitrarily large base points.
  • Twin admissibility: the twin offsets (0, 1) are admissible.
  • Twin primes: the conjecture for the twin offsets yields infinitely many twin primes.
  • Richards: the first conjecture (for all tuples) and the second conjecture (for all pairs x,y≥2x, y \ge 2x,y≥2) cannot both be true.

The chain assembles: admissibility is the gatekeeper (necessity and vanishing), the model integral and the singular series are the two analytic quantities the conjecture relates, positivity and divergence turn the asymptotic into infinitude, the twin case is the celebrated concrete consequence, and Richards' theorem fences off the second conjecture.

Significance

The prime kkk-tuple conjecture is the strongest concrete prediction about the distribution of primes that is consistent with current knowledge: it implies the twin prime conjecture, the Sophie Germain-type infinitudes, and every admissible pattern one can write down, each with a precise constant. It sits at the edge of the circle method — the same machinery that yields the ternary Goldbach theorem for additive patterns — and its obstruction is exactly the correlation between primes that current technology cannot rule in. A Lean formalization of the conjecture's statement, together with the surrounding structural facts, fixes the target unambiguously and gives solvers an attack path whose every waypoint is independently valuable: each milestone is a theorem of lasting interest in the theory of prime constellations, and the Richards incompatibility is a landmark result of 1974 that the community can be proud to carry.

Difficulty

The milestones span elementary number theory (residue coverage, admissibility, the twin-configuration check), real analysis (the divergence of the logarithmic integral), analytic number theory at the research frontier (the convergence and positivity of the singular series, via Mertens-type estimates), and combinatorial asymptotics for Richards' incompatibility. The admissibility lemmas are of moderate difficulty; the divergence of the model integral is a standard exercise in integral comparison; the positivity of the singular series requires the classical estimate that the Euler product converges on distinct offsets; the Richards milestone requires constructing, from the conjectured density of a suitable long admissible constellation, an interval carrying more primes than subadditivity permits — a research-grade formalization. The goal itself is one of the great open problems of number theory; the mission's value lies in the precisely stated target and the independently valuable waypoints, exactly the role of an OpenProblem mission.

Formalization scope

Every item quantifies only over the objects it needs — offset tuples, base points, primes, bounds; no item carries a vacuous hypothesis: the twin configuration is admissible, the conjunctions of the conjecture are satisfiable, and the vanishing and incompatibility statements are the intended degenerate truths. The fragment excludes the second Hardy–Littlewood conjecture as a provable target (Richards' theorem makes it a trap), excludes no case of the first conjecture (it is stated for every tuple, exactly as the source), and adds no hypothesis to the conjecture beyond the source's own. Nothing in the mission asserts the truth of the first conjecture or of the twin prime conjecture; it formalizes the statements precisely, together with the implications among them that are known.

Selected references

  • G. H. Hardy and J. E. Littlewood, Some problems of "Partitio numerorum"; III: On the expression of a number as a sum of primes, Acta Mathematica 44 (1923), pp. 1–70 — the two conjectures and the singular series.
  • I. Richards, On the Incompatibility of Two Conjectures Concerning Primes, Bulletin of the American Mathematical Society 80 (1974), pp. 419–438 — the incompatibility theorem.
  • Formal Conjectures project, HardyLittlewood.lean (2025) — the mission's source file, Apache 2.0.
  • Wikipedia, First Hardy–Littlewood conjecture and Second Hardy–Littlewood conjecture — the source file's own reference links.
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CombinatoricsComplexity Theory·Captain: Robin Kothari

Block Sensitivity vs. Sensitivity: Reach 2.075Open Problem

The quantitative sensitivity question

Sensitivity and block sensitivity measure how a Boolean function responds to changes in its input. They are central examples of query complexity measures: an algorithm learns an unknown input by querying its individual coordinates, while these measures describe how many changes the function can detect at a single input. Understanding their relationship helps distinguish the complexity caused by individual coordinate changes from the complexity caused by changes to groups of coordinates.

The Block Sensitivity vs. Sensitivity campaign tracks the largest certified separation exponent. Its classical benchmark is a quadratic separation. OpenAI problem 132 supplied a superquadratic construction and a Lean formalization in 2026. Subsequent campaign entries reached 2.0391, 2.05, and 2.0635. This entry establishes the exact exponent 2.075=83/402.075=83/402.075=83/40 using the same definitions and quantifiers.

Boolean functions and sensitive changes

A total Boolean function assigns an output bit to every input of nnn bits:

f:{0,1}n⟶{0,1}.f:\{0,1\}^n\longrightarrow\{0,1\}.f:{0,1}n⟶{0,1}.

For an input xxx and a coordinate set DDD, let xDx^DxD denote the input obtained by flipping precisely the coordinates in DDD. The sensitivity at an input counts the individual coordinates whose flips change the output:

s(f,x)=∣{i:f(x{i})≠f(x)}∣.s(f,x)=\bigl|\{i:f(x^{\{i\}})\ne f(x)\}\bigr|.s(f,x)=​{i:f(x{i})=f(x)}​.

The block sensitivity at an input, denoted bs(f,x)bs(f,x)bs(f,x), is the largest number of pairwise disjoint nonempty coordinate sets D1,…,DkD_1,\ldots,D_kD1​,…,Dk​ such that flipping any one of them changes the output at xxx. The sets are tested separately, always starting from the same input. The corresponding global measures are

s(f)=max⁡xs(f,x),bs(f)=max⁡xbs(f,x).s(f)=\max_x s(f,x),\qquad bs(f)=\max_x bs(f,x).s(f)=xmax​s(f,x),bs(f)=xmax​bs(f,x).

The maxima range over all inputs, including inputs on which the output is zero and inputs on which it is one. No monotonicity, symmetry, or restriction on the number of variables is imposed.

Target: exponent at least 2.075

For every real ε>0\varepsilon>0ε>0 and every integer S≥2S\ge2S≥2, establish the existence of a dimension nnn and a total Boolean function fff with

s(f)≥S,bs(f)≥s(f)83/40−ε.s(f)\ge S,\qquad bs(f)\ge s(f)^{83/40-\varepsilon}.s(f)≥S,bs(f)≥s(f)83/40−ε.

The campaign predicate SensitivityCampaign.AchievesExponent (2.075 : ℝ) states this exact proposition. The decimal is interpreted exactly, as 83/4083/4083/40, rather than as an approximate floating-point value. The function and dimension may depend on both the exponent loss ε\varepsilonε and the requested threshold SSS.

The threshold quantifier is essential: the target concerns arbitrarily large sensitivity. A small isolated function, or a collection of functions whose sensitivity stays bounded, does not by itself establish the campaign statement. The use of an arbitrary positive exponent loss agrees with the campaign's other entries and allows their values to be compared directly.

What this entry establishes

This result increases the certified exponent beyond the campaign's 2.0635 entry. It provides an intermediate achieved bound toward the separate 2.10 research target. It does not assert that 2.10 has been reached or identify the optimal exponent.

The complete Lean proof has compiled successfully, passed local kernel replay, and been accepted by Prove2Me. The verified theorem and full proof establish the stated target. Its supporting development includes nine-predicate sensitivity estimates, bounds on joint changes of nested predicates, finite labeling existence, disjoint sensitive-block witnesses, and an exact integer certificate. The accompanying proof explanation describes how these ingredients establish the stated target. The finite-certificate and logarithmic-score theorems from the campaign foundation remain referenced as reusable milestones.

The difficulty in improving the bound

A construction must have many disjoint sensitive blocks at one input while keeping sensitivity small at every input. A large block family supplies only the lower-bound half of this requirement. An input that makes many individual coordinates sensitive can invalidate the global upper bound even if the intended block-witness input behaves well.

Joint boundary behavior is another constraint: analyzing several related predicates independently can lose information about which changes can occur together. The formal proof therefore needs correct sensitivity estimates for the actual input-coordinate flips throughout the construction. Numerical growth estimates must also account for every fixed overhead before they can certify a finite exponent inequality.

Formalization scope and reusable foundations

The function type is (Fin n → Bool) → Bool. Sensitivity and block sensitivity use the existing OAI.Paper320 definitions, imported through Definitions.Def_SensitivityCampaign. Both measures are natural numbers defined using maxima over finite collections. The exponent comparison casts them to real numbers and uses real exponentiation. Since every requested witness has sensitivity at least two, the base of that power is positive.

The mission retains the shared campaign definitions without modifications. The two foundation milestones are SensitivityCampaign.finite_certificate, which turns suitable finite sensitivity and block-sensitivity bounds into the asymptotic target, and SensitivityCampaign.finite_certificate_log, which expresses the same interface using a logarithmic score. Their normalization and unbounded-sensitivity conclusions are part of their proved statements.

The supplied proof targets Lean 4.33.1 and Mathlib revision 0df444a360eaa60ab8c11dca51a86af692955474. The supporting assertions are proved in the submitted source; no conjectural lemma or numerical approximation is used as an assumption. The general transfer estimates and exact certificate provide material for subsequent improvements, while this mission's goal remains the fixed campaign value 2.075.

Selected references and credits

  • OpenAI, A superquadratic separation between sensitivity and block sensitivity, problem 132, 2026. Formalization and source links.
  • Prove2Me contributors, Separation exponent at least 2.0391, 2026. Accepted theorem and proof.
  • Robin Kothari, Separation exponent at least 2.05, 2026. Accepted theorem and proof.
  • abhishekdpseok, Separation exponent at least 2.0635, 2026. Accepted theorem and proof, submission f80a3f37-72fa-4d56-a094-3e4d351764f3. The present development reuses its foundation, including its earlier source credits.
  • Robin Kothari and Codex, Seven-level nine-state sensitivity certificate: exponent 2.075, 19 October 2026. Full Lean proof and mathematical explanation supplied with this entry.
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EconomicsOperations ResearchProbability·Captain: mikedeng1

Learning in a Post-Truth World: Below a Misinformation Threshold Bayesian Societies Mislearn No More Often than DeGroot Societies, and Above It Strictly More OftenResearch Paper

Motivation

People receive both informative reports and messages that are unrelated to the truth. A standard question in social learning is whether sharing beliefs helps a population identify the correct state. The question changes when everyone knows misinformation exists but does not know its ideological direction. Mostagir and Siderius study this setting and show that the ranking of two learning rules changes with the amount of misinformation: Bayesian updating can be at least as reliable at low levels, while simple averaging is more reliable at sufficiently high levels under full support. Their result is stated as Theorem 1 of the SSRN working paper, later published in Management Science.

The comparison matters for models of collective decisions because the same population, news quality, and misinformation distribution can lead to different rates of wrong terminal actions solely because the agents process others' beliefs differently. The paper's question is therefore about the behavior of learning rules, not just the accuracy of any one message. The mission covers the paper's regime comparison; its separate results on hazard rates, polarization, and targeting are outside this target.

Setting

The unknown state θ\thetaθ is either LLL or RRR. An organic message matches the state with probability p>1/2p>1/2p>1/2. A fraction q<1/2q<1/2q<1/2 of all messages consists of misinformation. Its split r∈[0,1]r\in[0,1]r∈[0,1] is the fraction of misinformation advocating RRR; rrr has distribution FFF with density fff. Agents start with heterogeneous prior probabilities x∈[0,1]x\in[0,1]x∈[0,1] of state RRR, distributed according to a continuous law HHH. The paper assumes these priors and the split are independent. All comparisons concern the limit of a large population, where the observed fraction of each message type is determined by θ\thetaθ and rrr (§2, pp. 4–6).

A DeGroot agent first updates on her own message while treating it as organic, using equations (1) and (2) of the paper. Thereafter agents average one another's beliefs. In the large-population model used by the proof, every agent reaches the same consensus π∞(θ,r)\pi_\infty(\theta,r)π∞​(θ,r): the HHH-average of the two face-value posteriors, weighted by the fractions of RRR and LLL messages. A Bayesian agent treats misinformation as possible and infers the message shares from the population's beliefs. The same observed share can be explained by the true state and split or by the other state with a different split. The posterior πB(θ,r,x)\pi_B(\theta,r,x)πB​(θ,r,x) weighs these two narratives according to their densities under FFF and the agent's prior xxx (proofs of Lemmas 1–2, pp. 18–19).

An agent's terminal action favors whichever state has posterior belief at least one half. A society mislearns at (θ,r)(\theta,r)(θ,r) when a positive HHH-mass of agents favors the wrong state; for DeGroot agents, who share a consensus, this is a single belief comparison. Write PB(θ)P_B(\theta)PB​(θ) and PD(θ)P_D(\theta)PD​(θ) for the FFF-probabilities of Bayesian and DeGroot mislearning. The paper studies both true states; the formulas for RRR mirror those for LLL.

Formalization targets

The main target is Theorem 1, p. 10. For every 1/2<p≤11/2<p\leq11/2<p≤1, set

q∗=2p−12p.q^*=\frac{2p-1}{2p}.q∗=2p2p−1​.

For every continuous symmetric prior law HHH on [0,1][0,1][0,1] and every split law FFF supplied by a density, the goal compares both states separately:

0<q<q∗⟹PB(θ)≤PD(θ),q∗<q<12,H,F fully supported on [0,1]⟹PD(θ)<PB(θ),θ∈{L,R}.\begin{aligned} 0<q<q^*&\quad\Longrightarrow\quad P_B(\theta)\leq P_D(\theta),\\ q^*<q<\tfrac12,\quad H,F\text{ fully supported on }[0,1] &\quad\Longrightarrow\quad P_D(\theta)<P_B(\theta), \end{aligned} \qquad\theta\in\{L,R\}.0<q<q∗q∗<q<21​,H,F fully supported on [0,1]​⟹PB​(θ)≤PD​(θ),⟹PD​(θ)<PB​(θ),​θ∈{L,R}.

The first comparison is non-strict because both mislearning probabilities can be zero, although the preprint uses the word “lower.” The value of q∗q^*q∗ comes from the paper's proof, which states the result with an existential threshold. The five milestones state the DeGroot and Bayesian mislearning cutoffs, the necessary misinformation level for Bayesian mislearning, the cutoff difference, and the resulting full-support probability formulas. Their source text and page numbers accompany the individual items.

Significance

The theorem isolates a regime in which adding misinformation changes the relative performance of the two learning rules. Under full support, the high-misinformation conclusion is strict: some split realizations cause Bayesian society to mislearn even while DeGroot society learns. The low-misinformation conclusion gives a uniform comparison over every allowed distribution of the split, without requiring its full support (Theorem 1 and proof, pp. 10, 20). These are statements about society-level mistakes, not a claim that an individual averaging rule is always more accurate.

The result has a published mathematical proof. It does not yet have a machine-checked proof in this development. Formalizing it requires a reusable interface for two-state misinformation models: a law of heterogeneous priors, a density for the split, the two narrative splits, posterior beliefs, and mislearning events. Those objects can also support the paper's later questions about the distributional shape of misinformation and the choice of targeting policy.

Difficulty

The obvious comparison of the two update rules at a fixed message fails to settle the result. DeGroot agents act on an average of face-value posteriors; Bayesian agents act on an agent-specific posterior after considering competing explanations of the same population message share. Thus the two groups can be wrong for different split realizations, and a statement about one representative belief does not give a society-level mislearning probability. The comparison must also distinguish a pointwise mistake at the edge of the split support from an event of positive probability. A second issue is that the converse direction of the printed Lemma 2 assumes agents with beliefs arbitrarily close to the extremes, which requires full prior support on [0,1][0,1][0,1] (Lemma 2 and proof, p. 19).

Formalization scope

Lean uses the paper's large-population formulas directly: π∞\pi_\inftyπ∞​ is an integral over HHH, and πB\pi_BπB​ is a density-weighted posterior over the two narrative splits. The Bayesian terminal belief is its period-two posterior; later observations add no information in this model. HHH is a probability measure concentrated on [0,1][0,1][0,1] with no atoms. FFF is given by a measurable nonnegative real density whose integral is one and whose support lies in [0,1][0,1][0,1]. Full support on an interval means that the density is bounded below there by a positive constant and is zero outside. Symmetry means invariance of HHH under x↦1−xx\mapsto1-xx↦1−x.

The formalized regime has 0<q<1/20<q<1/20<q<1/2 so the cutoffs involving division by qqq are defined as intended; the paper's misinformation-free case q=0q=0q=0 is an example outside this theorem. A belief of exactly 1/21/21/2 counts as wrong, matching the weak cutoff inequalities. Mislearning for Bayesian society requires a positive HHH-mass of wrong agents, and the final probabilities are extended nonnegative real measures of split events. The real posterior's zero-denominator default can arise outside the split support, which carries zero FFF-mass; pointwise Bayesian milestones restrict rrr to the support.

The model defines mislearning from posterior beliefs and the law of rrr, so the main theorem cannot be reduced to a comparison of cutoff formulas by definition. Solver contributions may establish measurability and integrability facts for the model, the cutoff lemmas, and the final comparison. The standing interval-support assumptions in the paper are narrowed to [0,1][0,1][0,1] where the theorem needs them; the main comparison does not fix arbitrary smaller support intervals.

Selected references

  • Mostagir, Mohamed, and James Siderius. Learning in a Post-Truth World. SSRN working paper 3879174, version of 2 July 2021; published in Management Science 68, 2022. SSRN preprint. The mission cites the preprint's page and theorem numbering.
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EconomicsOperations Research·Captain: mikedeng1

Agency or Wholesale? The Role of Retail Pass-Through: Under Nonnegative Cross-Brand Pass-Through Agency Selling Favors the E-tailer; Under Negative, Wholesale Is Cheaper iff θ^W < θ^B min{K^B, 1}Research Paper

Motivation

An online retailer may buy products from suppliers and resell them, or let suppliers sell directly while collecting a commission. The choice changes who sets retail prices and how a wholesale price change for one product affects the prices of competing products. In the first arrangement, the retailer sets all retail prices; in the second, suppliers set their own prices after the retailer chooses a commission. Hu, Zheng, and Pan study how this cross-brand retail pass-through changes the comparison between those arrangements. Their Proposition 2 identifies a sharp split: nonnegative cross-brand pass-through favors agency selling for the retailer, while negative pass-through can reverse the retail-price ordering. The question matters when a retailer must choose a contract for several competing products rather than evaluate a single supplier in isolation. Hu, Zheng, and Pan, SSRN preprint, §§3–5.

Setting

There are n≥2n\geq2n≥2 symmetric suppliers, each with marginal cost cs≥0c_s\geq0cs​≥0. At a common retail price ppp in an open positive interval DDD, the demand for one product is q(p)>0q(p)>0q(p)>0 and falls with price. Its demand sensitivity is

λ(p)=−q(p)q′(p).\lambda(p)=-\frac{q(p)}{q'(p)}.λ(p)=−q′(p)q(p)​.

The paper assumes that λ′(p)<1\lambda'(p)<1λ′(p)<1, that λ(p)[2−λ′(p)]\lambda(p)[2-\lambda'(p)]λ(p)[2−λ′(p)] has slope less than one, and that pλ′(p)≤λ(p)p\lambda'(p)\leq\lambda(p)pλ′(p)≤λ(p). These are the symmetric-price forms of its demand conditions A1, A3, and A4. The model also uses an aggregate diversion ratio ϵ\epsilonϵ: the fraction of the own-product demand response diverted to other suppliers. Under A1, 0≤ϵ<10\leq\epsilon<10≤ϵ<1. Hu, Zheng, and Pan, §§3.1–3.2, pp. 7–9.

Let a=∂pi/∂wia=\partial p_i/\partial w_ia=∂pi​/∂wi​ be own-brand pass-through and b=∂pj/∂wib=\partial p_j/\partial w_ib=∂pj​/∂wi​ for j≠ij\ne ij=i be cross-brand pass-through. The total response is a+(n−1)b=1/[1−λ′(pW)]a+(n-1)b=1/[1-\lambda'(p^W)]a+(n−1)b=1/[1−λ′(pW)]. The suppliers' conduct parameters under wholesale and agency selling are respectively

θW=(1−ϵ)[a+(n−1)b]a−ϵb,θB=1−ϵ.\theta^W=\frac{(1-\epsilon)[a+(n-1)b]}{a-\epsilon b},\qquad \theta^B=1-\epsilon.θW=a−ϵb(1−ϵ)[a+(n−1)b]​,θB=1−ϵ.

The wholesale retail price pWp^WpW and agency retail price pBp^BpB are any solutions, in DDD, of the two equations of Lemma 1 after the retailer's marginal cost crc_rcr​ is normalized to zero. The corresponding wholesale price is wW=pW−λ(pW)w^W=p^W-\lambda(p^W)wW=pW−λ(pW), and the agency commission rate is αB=cs/[pB−θBλ(pB)]\alpha^B=c_s/[p^B-\theta^B\lambda(p^B)]αB=cs​/[pB−θBλ(pB)]. The profits πrW,πiW,πrB,πiB\pi_r^W,\pi_i^W,\pi_r^B,\pi_i^BπrW​,πiW​,πrB​,πiB​ come from the respective wholesale and agency contract objectives. Finally, §5 defines

KB=αB1−λ′(pB)[1+λ(pB)−pBλ′(pB)pB−θBλ(pB)].K^B=\frac{\alpha^B}{1-\lambda'(p^B)}\left[1+\frac{\lambda(p^B)-p^B\lambda'(p^B)}{p^B-\theta^B\lambda(p^B)}\right].KB=1−λ′(pB)αB​[1+pB−θBλ(pB)λ(pB)−pBλ′(pB)​].

These are the quantities in Proposition 2. Hu, Zheng, and Pan, Lemma 1, p. 11; §5, p. 13.

Formalization targets

Nonnegative cross-brand pass-through

For every pair of equilibrium prices pW,pBp^W,p^BpW,pB satisfying Lemma 1's equations, Proposition 2(i) asserts that b≥0b\geq0b≥0 implies

pB≤pW,πrB≥πrW,πiB≤πiW.p^B\leq p^W,\qquad \pi_r^B\geq\pi_r^W,\qquad \pi_i^B\leq\pi_i^W.pB≤pW,πrB​≥πrW​,πiB​≤πiW​.

The milestone list includes Proposition 1's comparison of θW\theta^WθW and θB\theta^BθB, the price ordering, and the auxiliary profit comparisons in the authors' proof. Hu, Zheng, and Pan, Propositions 1–2, pp. 12–13; Appendix B, pp. 26–27.

Negative cross-brand pass-through

When b<0b<0b<0, the price part of Proposition 2(ii) gives the exact criterion

pW<pB⟺θW<θBmin⁡{KB,1}.p^W<p^B\quad\Longleftrightarrow\quad\theta^W<\theta^B\min\{K^B,1\}.pW<pB⟺θW<θBmin{KB,1}.

The milestone for this case is the authors' rewrite of condition (8) in terms of KBK^BKB. The paper also says that wholesale selling can be more profitable for the retailer and agency selling may benefit suppliers; those are existence observations illustrated by its examples and are outside this mission's goal. Hu, Zheng, and Pan, Proposition 2(ii), p. 13; Appendix B, p. 27.

Significance

Proposition 2 separates two forces in the contract choice. Agency selling avoids the retailer's wholesale markup, while the sign of cross-brand pass-through changes the relative intensity of supplier competition. Under nonnegative pass-through, the paper obtains simultaneous comparisons of prices and both parties' profits. Under negative pass-through, the threshold KBK^BKB gives a precise condition for a reversal in retail prices. These conclusions let the two contracts be compared using measurable pass-through responses and the demand curve, instead of treating the number of competing suppliers alone as decisive. Hu, Zheng, and Pan, §§4–5, pp. 12–13.

The result is proved in the source paper. This mission supplies compiled Lean statements and a common definition layer, but no machine-checked proofs of the theorem or its milestones yet. Completing it would verify the equilibrium comparisons under explicit demand and denominator conditions. The auxiliary monotonicity and profit identities can also be reused when studying the paper's later results on supplier preferences and welfare.

Difficulty

The immediate comparison of the two equilibrium price equations does not determine which price is larger: the conduct parameter differs between contracts, and the agency equation contains a cost term with a squared denominator. The paper's assumptions control the slopes of two demand-sensitivity expressions, while the profit comparisons require different auxiliary curves for suppliers and the retailer. In the negative pass-through case, the condition involving KBK^BKB must still be combined with the conduct-parameter ordering. These are substantive inequalities; simply unfolding the profit definitions does not give Proposition 2. Hu, Zheng, and Pan, Appendix B, pp. 26–27.

Formalization scope

Lean uses real-valued demand on an open, order-connected interval D⊂(0,∞)D\subset(0,\infty)D⊂(0,∞) and a natural-number supplier count n≥2n\geq2n≥2, cast to the reals in formulas. Derivatives are ordinary derivatives on DDD. The smoothness assumption is C3C^3C3 there because A3 differentiates an expression containing λ′\lambda'λ′. Positive demand is explicit; A1 requires q′<0q'<0q′<0. The strict bound ϵ<1\epsilon<1ϵ<1 follows from the strict total-demand decrease in A1, although the paper prints the weaker interval [0,1][0,1][0,1]. The expressions divide only where their denominators are positive: a−ϵb>0a-\epsilon b>0a−ϵb>0, pB−θBλ(pB)>0p^B-\theta^B\lambda(p^B)>0pB−θBλ(pB)>0, and 1−λ′(pB)>01-\lambda'(p^B)>01−λ′(pB)>0 by A3. The paper uses θW∈[0,1]\theta^W\in[0,1]θW∈[0,1] in its proof, so that bound is also explicit. The retailer's marginal cost is fixed to cr=0c_r=0cr​=0 as on p. 12. Hu, Zheng, and Pan, A1–A4, pp. 7–8; Lemma 1, p. 11; Proposition 2 proof, p. 26.

The n-product demand system and Stackelberg games are represented by their conduct-parameter symmetric equilibrium equations from Lemma 1. Every theorem concerns every pair of prices satisfying those equations in DDD; no existence or uniqueness of such a pair is presumed. The original game and A5's invariant-conduct assumption are not reconstructed. Profits remain the original contract objectives at symmetric prices, rather than being defined by the reduced forms that the proof seeks to establish. The definition layer, demand calculus, and milestone inequalities are all open to proof contributions; the contract-profit identities must be derived from their objective definitions.

Selected references

  • Hu, H., Zheng, Q., and Pan, X. A., Agency or Wholesale? The Role of Retail Pass-Through, SSRN preprint 3724934, 2021 revision; published in Management Science, 2022. SSRN; DOI.
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Quantum Information·Captain: Goku

Entanglement-assisted capacity of a quantum channel and the reverse Shannon theoremResearch Paper

Motivation

The entanglement-assisted classical capacity of a noisy quantum channel is the amount of information per channel use that can be sent over the channel in the limit of many uses of the channel, assuming that the sender and receiver have access to the resource of shared quantum entanglement, which may be used up by the communication protocol. We show that this capacity is given by an expression parallel to that for the capacity of a purely classical channel: i.e., the maximum, over channel inputs ρ\rhoρ, of the entropy of the channel input plus the entropy of the channel output minus their joint entropy, the latter being defined as the entropy of an entangled purification of ρ\rhoρ after half of it has passed through the channel. We calculate entanglement-assisted capacities for two interesting quantum channels, the qubit amplitude damping channel and the bosonic channel with amplification/attenuation and Gaussian noise. We discuss how many independent parameters are required to completely characterize the asymptotic behavior of a general quantum channel, alone or in the presence of ancillary resources such as prior entanglement. In the classical analog of entanglement assisted communication--communication over a discrete memoryless channel (DMC) between parties who share prior random information--we show that one parameter is sufficient, i.e., that in the presence of prior shared random information, all DMC's of equal capacity can simulate one another with unit asymptotic efficiency.

This mission is the statement-level formalization of Entanglement-assisted capacity of a quantum channel and the reverse Shannon theorem (arXiv:quant-ph/0106052v2). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

12 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Theorem 1: entanglement-assisted classical capacity (Theorem 1: entanglement-assisted classical capacity, PDF p. 8). 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

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

  • §I: a channel with Q > 0 but C = C_E: Counted noisy-channel steps interleaved with accepted finite LOCC, and source-compatible operational quantum-transmission capacities Q2, Q and unassisted C (hard)
  • §III: finite-dimensional approximation for energy-constrained Gaussian channels: Positive trace-one multimode Fock states, spectral entropy/purification, reference-extended Gaussian CPTP maps, photon-energy constraints, and energy-constrained operational assisted capacity (hard)
  • §III.A Eq.(78): large-noise enhancement factor: Positive trace-one multimode Fock states, spectral entropy/purification, reference-extended Gaussian CPTP maps, photon-energy constraints, and energy-constrained operational assisted capacity (hard)
  • Fig.6: small-signal Gaussian capacity asymptotics: Positive trace-one multimode Fock states, spectral entropy/purification, reference-extended Gaussian CPTP maps, photon-energy constraints, and energy-constrained operational assisted capacity (hard)
  • §III.A Eqs.(79)–(80): coherent-state bounds, with corrected regimes: Positive trace-one multimode Fock states, spectral entropy/purification, reference-extended Gaussian CPTP maps, photon-energy constraints, and energy-constrained operational assisted capacity (hard)
  • §III.A: fixed signal-to-noise high-energy classical limit: Positive trace-one multimode Fock states, spectral entropy/purification, reference-extended Gaussian CPTP maps, photon-energy constraints, and energy-constrained operational assisted capacity (hard)
  • §III.A Eqs.(82),(86): teleportation and dense-coding bounds: Positive trace-one multimode Fock states, spectral entropy/purification, reference-extended Gaussian CPTP maps, photon-energy constraints, and energy-constrained operational assisted capacity (hard)
  • §III.A Eqs.(83)–(85),(87): optimized squeezed-state bounds: Positive trace-one multimode Fock states, spectral entropy/purification, reference-extended Gaussian CPTP maps, photon-energy constraints, and energy-constrained operational assisted capacity (hard)
  • Corollary 2: constrained sources (source obstruction): A true source hypothesis sufficient for constrained-source tail efficiency (source-ambiguity)
  • §V: proposed feedback consequence of the QRSC: Source-pinned composable quantum simulation criterion for adaptive feedback substitution (source-ambiguity)

Selected references

  • Entanglement-assisted capacity of a quantum channel and the reverse Shannon theorem, arXiv:quant-ph/0106052v2, https://arxiv.org/abs/quant-ph/0106052v2
21 thms3 active usersReviewed
Quantum Information·Captain: Goku

The asymptotic entanglement cost of preparing a quantum stateResearch Paper

Motivation

We give a detailed proof of the conjecture that the asymptotic entanglement cost of preparing a bipartite state \rho is equal to the regularized entanglement of formation of \rho.

This mission is the statement-level formalization of The asymptotic entanglement cost of preparing a quantum state (arXiv:quant-ph/0008134v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

11 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Entanglement cost equals regularized entanglement of formation (Theorem 1 / Eq.(7), continued on PDF p.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.

Deferred results

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

  • Introduction, general monotone paragraph after Eq.(5): A specified normalization or asymptotic singlet-unit upper bound for the general function f. (source-ambiguity)

Selected references

  • The asymptotic entanglement cost of preparing a quantum state, arXiv:quant-ph/0008134v1, https://arxiv.org/abs/quant-ph/0008134v1
20 thms3 active usersReviewed
Quantum Information·Captain: Goku

Entanglement-of-formation potentials for feedback-assisted classical communication and randomness distillationResearch Paper

Motivation

We develop entanglement-of-formation potentials for feedback-assisted classical communication and one-way randomness distillation. For a finite-dimensional quantum channel without initial shared entanglement, an exact amortization theorem bounds the increase of message information plus entanglement remaining across the communicating laboratories. This proves a classical-feedback capacity bound using a mixed-convex-roof expression previously studied by Winter and Yang in the context of potential capacities. We determine the capacity of flagged mixtures of noiseless and entanglement-breaking channels, improve a published depolarizing-channel converse, and evaluate the new bound exactly for the amplitude damping channel. A state analogue gives a finite-blocklength upper bound on the net shared randomness obtainable with one-way classical communication. Amplitude-damping Choi states provide exact benchmarks, while a full-rank generalized amplitude-damping Choi state demonstrates a useful improvement where we do not evaluate the operational rate exactly. We also distinguish one-way from two-way randomness distillation: a two-round weak-measurement protocol strictly exceeds the exact one-way rate of every nontrivial qubit isotropic state. The protocol preserves quantum side information during its first decoding and extracts additional randomness in the reverse direction. This shows why the one-way state potential is not a general two-way converse. Together, these results establish a common entanglement-based approach to sharper communication and randomness bounds, while revealing how retained quantum correlations enable two-way distillation to surpass one-way limits. △ Less

This mission is the statement-level formalization of Entanglement-of-formation potentials for feedback-assisted classical communication and randomness distillation (arXiv:2610.04831v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

27 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Proposition 2.1: cardinality and attainment (Proposition 2.1: cardinality and attainment, PDF p. 12). 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

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

  • Theorem 4.3: classical-feedback capacity bound (abstract seed): A semantic n-use feedback code and its maximum-error finite-use capacity and inf-error liminf capacity (hard)
  • Lemma 3.1: monotonicity under free operations: Message/transcript cq states, lawful message-controlled Alice and transcript-controlled Bob free operations, and their composition relation (hard)
  • Proposition 5.3: tensor products and regularization: A semantic n-use feedback code and its maximum-error finite-use capacity and inf-error liminf capacity (hard)
  • Theorem 6.1: exact flagged-channel capacity: A semantic n-use feedback code and its maximum-error finite-use capacity and inf-error liminf capacity (hard)
  • Theorem 8.2: exact damping evaluation: A semantic n-use feedback code and its maximum-error finite-use capacity and inf-error liminf capacity (hard)
  • Theorem 9.2: finite-blocklength one-way randomness: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Proposition 10.1: damping-source potential: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Proposition 11.1: one-way isotropic benchmark: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Theorem 12.1: two-round isotropic rate: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Corollary 12.2: strict two-way separation: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Flagged depolarizing simulation bound: A semantic n-use feedback code and its maximum-error finite-use capacity and inf-error liminf capacity (hard)
  • Analytic depolarizing converse improvement: The channel beta feasible set (B.1) and limiting channel Upsilon minimization over arbitrary completely positive comparison maps; A semantic n-use feedback code and its maximum-error finite-use capacity and inf-error liminf capacity (hard)
  • Fixed positive formation weights cannot close the depolarizing gap: The eta-weighted message/transcript potential and a computed near-pure Pauli-orbit one-use experiment; Message/transcript cq states, lawful message-controlled Alice and transcript-controlled Bob free operations, and their composition relation (hard)
  • Jump-flagged damping transmits a perfect bit: A semantic n-use feedback code and its maximum-error finite-use capacity and inf-error liminf capacity (hard)
  • Sharper converse with exactly uniform Alice key: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Derived forward/reverse damping-source rates: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Thermal operational interval and finite-error bound: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Old state-Upsilon lower certificates at thermal source: The state Upsilon_A/Upsilon_B comparison sets (10.38)-(10.39), with support-aware bit-valued Umegaki divergence on nonnormalized positive comparison operators (hard)
  • Exact-component upper bound for thermal family: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Perturbation potential bound and achievable rate: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Explicit perturbed-source improvement: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates; The state Upsilon_A/Upsilon_B comparison sets (10.38)-(10.39), with support-aware bit-valued Umegaki divergence on nonnormalized positive comparison operators (hard)
  • One-way potential cannot upper-bound two-way extraction: One-way and finite-round two-way LOCC randomness protocols, their squared-fidelity acceptance law, alphabet-size communication charge, and inf-error liminf rates (hard)
  • Appendix B.1: beta for twirled comparison maps: Source ambiguity: redundant orthogonal Choi sector when d=1 (source-ambiguity)
  • Appendix B.2: general depolarizing Upsilon formula: The channel beta feasible set (B.1) and limiting channel Upsilon minimization over arbitrary completely positive comparison maps (hard)
  • Appendix E.1: state-converse supporting hyperplanes: The state Upsilon_A/Upsilon_B comparison sets (10.38)-(10.39), with support-aware bit-valued Umegaki divergence on nonnormalized positive comparison operators and the natural-matrix-log derivative/supporting functional (hard)
  • Appendix E.3: transport of certificates under noise: The state Upsilon_A/Upsilon_B comparison sets (10.38)-(10.39), with support-aware bit-valued Umegaki divergence on nonnormalized positive comparison operators and the reference certificate operators under perturbation (hard)

Selected references

  • Entanglement-of-formation potentials for feedback-assisted classical communication and randomness distillation, arXiv:2610.04831v1, https://arxiv.org/abs/2610.04831v1
35 thms3 active usersReviewed
Quantum Information·Captain: Goku

A father protocol for quantum broadcast channelsResearch Paper

Motivation

A new protocol for quantum broadcast channels based on the fully quantum Slepian-Wolf protocol is presented. The protocol yields an achievable rate region for entanglement-assisted transmission of quantum information through a quantum broadcast channel that can be considered the quantum analogue of Marton's region for classical broadcast channels. The protocol can be adapted to yield achievable rate regions for unassisted quantum communication and for entanglement-assisted classical communication; in the case of unassisted transmission, the region we obtain has no independent constraint on the sum rate, only on the individual transmission rates. Regularized versions of all three rate regions are provably optimal.

This mission is the statement-level formalization of A father protocol for quantum broadcast channels (arXiv:quant-ph/0612155v4). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

10 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Entanglement-assisted broadcast father inner region (Theorem 2 / Eq. (9), PDF p. 4). 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

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

  • VI.C, asserted multiparty one-shot extension: A numerical multiparty one-shot trace-norm error functional, its aggregation constants, and the complete quantifier/decoder conclusion. (source-ambiguity)

Selected references

  • A father protocol for quantum broadcast channels, arXiv:quant-ph/0612155v4, https://arxiv.org/abs/quant-ph/0612155v4
20 thms3 active usersReviewed
🏆Completed
Quantum Information·Captain: Goku

Optimum Quantum Error Recovery using Semidefinite ProgrammingResearch Paper

Motivation

Quantum error correction (QEC) is an essential element of physical quantum information processing systems. Most QEC efforts focus on extending classical error correction schemes to the quantum regime. The input to a noisy system is embedded in a coded subspace, and error recovery is performed via an operation designed to perfectly correct for a set of errors, presumably a large subset of the physical noise process. In this paper, we examine the choice of recovery operation. Rather than seeking perfect correction on a subset of errors, we seek a recovery operation to maximize the entanglement fidelity for a given input state and noise model. In this way, the recovery operation is optimum for the given encoding and noise process. This optimization is shown to be calculable via a semidefinite program (SDP), a well-established form of convex optimization with efficient algorithms for its solution. The error recovery operation may also be interpreted as a combining operation following a quantum spreading channel, thus providing a quantum analogy to the classical diversity combining operation.

This mission is the statement-level formalization of Optimum Quantum Error Recovery using Semidefinite Programming (arXiv:quant-ph/0606035v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

11 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Optimum recovery is an attained semidefinite program (Abstract; IV, Eq. (22): optimum entanglement-fidelity recovery is an attained SDP, PDF p. 4). 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:

  • VI A and Fig. 2: numerical five-qubit amplitude-damping recovery comparison: Certified semantics for the approximate small-damping numerical fit and recovery comparison (source-ambiguity)
  • VI B and Fig. 3: numerical four-qubit amplitude-damping recovery comparison: Certified semantics for the approximate small-damping numerical fit and recovery comparison (source-ambiguity)

Selected references

  • Optimum Quantum Error Recovery using Semidefinite Programming, arXiv:quant-ph/0606035v1, https://arxiv.org/abs/quant-ph/0606035v1
16 thms3 active usersReviewed
🏆Completed
Quantum Information·Captain: Goku

Classification and implementation of unitary-equivariant and permutation-invariant quantum channelsResearch Paper

Motivation

Many quantum information tasks use inputs of the form ρ⊗m\rho^{\otimes m}ρ⊗m, which naturally induce permutation and unitary symmetries. We classify all quantum channels that respect both symmetries - i.e. unitary-equivariant and permutation-invariant quantum channels from (Cd)⊗m(\mathbb{C}^{d})^{\otimes m}(Cd)⊗m to (Cd)⊗n(\mathbb{C}^{d})^{\otimes n}(Cd)⊗n - via their extremal points. Operationally, each extremal quantum channel factors as unitary Schur sampling →\rightarrow→ an irrep-level unitary-equivariant quantum channel →\rightarrow→ the adjoint unitary Schur sampling. We give a streaming implementation ansatz that uses an efficient streaming implementation of unitary Schur sampling together with a resource-state primitive, and we apply it to state symmetrization, symmetric cloning, and purity amplification. In these applications we obtain polynomial-time algorithms with exponential memory improvements in m,nm,nm,n. Further, for symmetric cloning we present, to our knowledge, the first efficient (polynomial-time) algorithm with explicit memory and gate bounds.

This mission is the statement-level formalization of Classification and implementation of unitary-equivariant and permutation-invariant quantum channels (arXiv:2510.08154v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

2 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Choi commutants characterize both channel symmetries (Proposition 4, PDF p. 16). 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

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

  • Theorem 1 / Contribution I: extremal classification and operational factorization: Concrete signed-staircase SU(d) irreps with fixed orthonormal CG multiplicity coordinates, conjugate input factors, and the actual isometry I of Eq.(45). (hard)
  • Theorem 2 / Contribution II: resource-assisted streaming ansatz: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. Resource-path embeddings and their supplied access model. (hard)
  • Theorem 3 / Contribution III: three streaming applications: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. (hard)
  • Theorem 5: all channels via positive multiplicity blocks: Concrete signed-staircase SU(d) irreps with fixed orthonormal CG multiplicity coordinates, conjugate input factors, and the actual isometry I of Eq.(45). (hard)
  • Corollary 6: exact extreme-point parametrization: Concrete signed-staircase SU(d) irreps with fixed orthonormal CG multiplicity coordinates, conjugate input factors, and the actual isometry I of Eq.(45). (hard)
  • Proposition 7: claimed trace adjoint and normalized reconstruction: Ordinary trace adjoint versus normalized reconstruction Eq.(58). (source-ambiguity)
  • Theorem 8: operational factorization: Actual USS, normalized R, and CG-defined conditional irrep channel. (hard)
  • Proposition 9: path resources realize an irrep embedding: Iterated simple/dual CG path transform I_mu, mixed Schur transform, and derived multiplicity comparison J. (hard)
  • Proposition 10: length-restricted simple and dual CG costs: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. Length-restricted simple and dual CG transforms. (hard)
  • Proposition 11: streaming path embedding with explicit access costs: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. Supplied coherent path resource storage and retrieval. (hard)
  • Proposition 12 (Theorem 1 of [17]): streaming USS: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. The actual unitary Schur sampling channel. (hard)
  • Proposition 13: streaming normalized Schur reconstruction: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. Corrected uniform GT sampler and normalized Schur reconstruction. (hard)
  • Theorem 14: streaming composition with irrep-stage costs: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. Fixed implementations of the CG embedding branches. (hard)
  • Corollary 15: streaming state symmetrization: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. (hard)
  • Corollary 16: streaming optimal symmetric cloning: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. A circuit on the symmetric input operator algebra. (hard)
  • Corollary 17: streaming one-output purity amplification: Executable adaptive streaming qubit circuits in the CNOT/H/Z^(1/4) gate set, with GT encodings, live-wire memory, gates, emitted-output semantics, and restricted diamond error. Normalized one-box Pieri embedding on concrete Schur images. (hard)
  • Proposition 18: LR symmetries and compatible vectorized CG choices: Globally coherent multiplicity/basis transport under flips and dualization. (source-ambiguity)
  • Theorem 19: all extremal irrep channels and three equivalent formulas: Signed SU(d) irrep channels and locally compatible vectorized CG intertwiners. (hard)
  • Theorem 20 (Section 2 of [29]): uniform GT path sampling: Executable corrected GNW hook-walk sampler and its GT-path labeling. (hard)
  • Proposition 21: weighted hook-walk equivalence and arithmetic costs: Corrected contracted weighted hook walk with an actual random arithmetic program and its costs. (hard)

Selected references

  • Classification and implementation of unitary-equivariant and permutation-invariant quantum channels, arXiv:2510.08154v1, https://arxiv.org/abs/2510.08154v1
7 thms3 active usersReviewed
🏆Completed
AnalysisOperations ResearchOptimization·Captain: mikedeng1

Personalized Robo-Advising: Enhancing Investment Through Client Interaction: The Approximate Personalization Measure Has a Unique Optimal Time Between Interactions, Increasing in Behavioral BiasResearch Paper

How often should a robo-advisor talk to its client?

A robo-advisor is an automated portfolio manager. It invests a client's wealth according to a model of the client's risk preferences, and it learns those preferences by interacting with the client: questionnaires, check-ins, requests to confirm or revise a risk profile. The design question of how often such a system should query its client is practical: each interaction updates the advisor's view of a preference that drifts over time, but each interaction is also exposed to the client's momentary reaction to recent market moves.

Capponi, Ólafsson and Zariphopoulou (Management Science 68(4), 2022; read here as arXiv:1911.01391v2) model this trade-off. Their Proposition 5.1 gives a closed-form approximation of how well the portfolio tracks the client's true risk aversion as a function of the time between interactions, and shows that this approximation has a unique optimal interaction time whose position responds monotonically to the model's parameters. This mission formalizes part (ii) of that proposition and the comparative statics (5.6).

Setting

Time is discrete. The client's true risk aversion γnC\gamma^C_nγnC​ evolves over the investment horizon; in each period it receives, with probability pϵ∈[0,1]p_\epsilon \in [0,1]pϵ​∈[0,1], an idiosyncratic shock σϵWn−σϵ2/2\sigma_\epsilon W_n - \sigma_\epsilon^2/2σϵ​Wn​−σϵ2​/2 with WnW_nWn​ standard Gaussian and σϵ>0\sigma_\epsilon > 0σϵ​>0, and no shock otherwise (p. 17). The robo-advisor and client interact every ϕ≥1\phi \ge 1ϕ≥1 periods. At an interaction the client communicates a risk-aversion parameter that is distorted by a behavioral bias: it is the true value multiplied by e−β⋅(average excess market return since the last interaction)e^{-\beta \cdot(\text{average excess market return since the last interaction})}e−β⋅(average excess market return since the last interaction), where the coefficient β≥0\beta \ge 0β≥0 measures the strength of the bias (eq. (5.2), pp. 17–18). Between interactions the advisor keeps using the last communicated value. Market returns have volatility σ(y)>0\sigma(y) > 0σ(y)>0 in economic state yyy, and σ0:=σ(Y0)\sigma_0 := \sigma(Y_0)σ0​:=σ(Y0​) is the volatility in the initial state.

The personalization measure (5.4) is the expected time-average relative error between the advisor's risk tolerance 1/γn1/\gamma_n1/γn​ and the client's 1/γnC1/\gamma^C_n1/γnC​,

R(ϕ,β)=E[1T∑n=0T−1∣1/γn−1/γnC1/γnC∣].\mathcal R(\phi,\beta) = \mathbb E\Big[\frac1T\sum_{n=0}^{T-1}\Big|\frac{1/\gamma_n - 1/\gamma^C_n}{1/\gamma^C_n}\Big|\Big].R(ϕ,β)=E[T1​n=0∑T−1​​1/γnC​1/γn​−1/γnC​​​].

Lower is better. Proposition 5.1(i) shows that R\mathcal RR is, up to error terms, a multiple of the approximate personalization measure

R~(ϕ,β)=2π(βσ0ϕ(1−ϕ−12pϵ)+β2σ02ϕ+σϵ2  ϕ−12pϵ).\widetilde{\mathcal R}(\phi,\beta) = \sqrt{\frac{2}{\pi}}\left(\frac{\beta\sigma_0}{\sqrt{\phi}}\Big(1-\frac{\phi-1}{2}p_\epsilon\Big) + \sqrt{\frac{\beta^2\sigma_0^2}{\phi}+\sigma_\epsilon^2}\;\frac{\phi-1}{2}p_\epsilon\right).R(ϕ,β)=π2​​​ϕ​βσ0​​(1−2ϕ−1​pϵ​)+ϕβ2σ02​​+σϵ2​​2ϕ−1​pϵ​​.

The first term is the bias cost, which shrinks as interactions become rarer (the bias averages returns over a longer window); the second is the staleness cost, which grows with the number of shocks missed between interactions. The mission is about R~\widetilde{\mathcal R}R, as Proposition 5.1(ii) is. In Lean the parameters are a structure Params with fields sig0 (σ0\sigma_0σ0​), pe (pϵp_\epsilonpϵ​), se (σϵ\sigma_\epsilonσϵ​), β, and R~\widetilde{\mathcal R}R is Rtilde P φ.

Formalization targets

Goal: Proposition 5.1(ii) and (5.6)

Assume σ0>0\sigma_0 > 0σ0​>0, σϵ>0\sigma_\epsilon > 0σϵ​>0, pϵ∈[0,1]p_\epsilon \in [0,1]pϵ​∈[0,1], β≥0\beta \ge 0β≥0 and β+pϵ>0\beta + p_\epsilon > 0β+pϵ​>0. Then

arg⁡min⁡ϕ≥1R~(ϕ,β)={1,β=0,ϕ0∈[1,∞),β>0, pϵ>0,∞,pϵ=0,\arg\min_{\phi\ge1}\widetilde{\mathcal R}(\phi,\beta) = \begin{cases} 1, & \beta = 0,\\ \phi_0\in[1,\infty), & \beta>0,\ p_\epsilon>0,\\ \infty, & p_\epsilon = 0,\end{cases}argϕ≥1min​R(ϕ,β)=⎩⎨⎧​1,ϕ0​∈[1,∞),∞,​β=0,β>0, pϵ​>0,pϵ​=0,​

and ϕ0\phi_0ϕ0​ is increasing in β\betaβ and σ0\sigma_0σ0​ and decreasing in pϵp_\epsilonpϵ​ and σϵ\sigma_\epsilonσϵ​ (5.6). "arg⁡min⁡=∞\arg\min = \inftyargmin=∞" means that no ϕ≥1\phi \ge 1ϕ≥1 is a minimizer, R~\widetilde{\mathcal R}R decreases strictly on [1,∞)[1,\infty)[1,∞) and tends to its infimum 000.

Milestones

The proof (Appendix C, p. 46) works with the bracket f=π/2 R~f = \sqrt{\pi/2}\,\widetilde{\mathcal R}f=π/2​R and an auxiliary function ggg with f′(ϕ)=12βσ0pϵϕ−2g(ϕ)f'(\phi) = \tfrac12\beta\sigma_0p_\epsilon\phi^{-2}g(\phi)f′(ϕ)=21​βσ0​pϵ​ϕ−2g(ϕ). The milestones are its displayed claims, in order: f≥0f \ge 0f≥0; the two degenerate cases pϵ=0p_\epsilon = 0pϵ​=0 and β=0\beta = 0β=0; the factorization of f′f'f′; the value of f′(1)f'(1)f′(1) and the criterion f′(1)≥0  ⟺  pϵσϵ2/(β2σ02)≥2+1/pϵf'(1) \ge 0 \iff p_\epsilon\sigma_\epsilon^2/(\beta^2\sigma_0^2) \ge 2 + 1/p_\epsilonf′(1)≥0⟺pϵ​σϵ2​/(β2σ02​)≥2+1/pϵ​; the sufficient condition pϵσϵ/(βσ0)<1⇒∂ϕR~∣ϕ=1<0p_\epsilon\sigma_\epsilon/(\beta\sigma_0) < 1 \Rightarrow \partial_\phi\widetilde{\mathcal R}|_{\phi=1} < 0pϵ​σϵ​/(βσ0​)<1⇒∂ϕ​R∣ϕ=1​<0 of p. 22; the lower bound g′(ϕ)≥12ϕ−1/2g(1)g'(\phi) \ge \tfrac12\phi^{-1/2}g(1)g′(ϕ)≥21​ϕ−1/2g(1), which settles the corner case g(1)≥0g(1)\ge 0g(1)≥0; and the interior case g(1)<0g(1) < 0g(1)<0, where ggg is strictly convex, tends to ∞\infty∞, and has a unique zero at which fff is minimized.

Significance

The result gives the model's two qualitative predictions in exact form. Without behavioral bias the advisor should interact at every period; without idiosyncratic shocks it should never interact; when both are present there is a single best interaction frequency, and it moves in the economically expected direction: more bias or more volatile markets call for rarer interaction, more frequent or larger preference shocks call for more frequent interaction. The p. 22 criterion gives a checkable condition, in terms of pϵσϵp_\epsilon\sigma_\epsilonpϵ​σϵ​ against βσ0\beta\sigma_0βσ0​, under which interacting at every period is not optimal.

The proof in the paper is a sketch. The convexity of ggg in the interior case is asserted ("it can be shown"), and the comparative statics (5.6) are stated as following from "the form of the function fff". As printed, (5.6) asserts strict signs of partial derivatives of ϕ0\phi_0ϕ0​, which fail on the open parameter region where the minimizer sits at the corner ϕ0=1\phi_0 = 1ϕ0​=1 (there ϕ0\phi_0ϕ0​ is locally constant). A machine-checked proof therefore supplies the missing convexity argument and the corrected comparative statics. No part of the proposition is known to be formalized.

Difficulty

The function R~\widetilde{\mathcal R}R mixes ϕ−1/2\phi^{-1/2}ϕ−1/2, ϕ1/2\phi^{1/2}ϕ1/2 and a square root of β2σ02/ϕ+σϵ2\beta^2\sigma_0^2/\phi + \sigma_\epsilon^2β2σ02​/ϕ+σϵ2​. The sign of its derivative is not visible from the formula, and the paper's sign analysis passes through ggg; the paper's claim that ggg is strictly convex has no written proof. The comparative statics are not a differentiable implicit-function computation either: the minimizer switches between the corner ϕ=1\phi = 1ϕ=1 and an interior root of ggg, and the monotonicity must hold across that switch. The obvious move of differentiating the first-order condition g(ϕ0)=0g(\phi_0) = 0g(ϕ0​)=0 in the parameters covers only the interior region and says nothing at the corner.

Formalization scope

All quantities are real. The time between interactions ϕ\phiϕ is a real variable on [1,∞)[1,\infty)[1,∞): the model uses integer ϕ\phiϕ, but Proposition 5.1 differentiates in ϕ\phiϕ and places ϕ0\phi_0ϕ0​ in [1,∞)[1,\infty)[1,∞). The standing ranges σ0>0\sigma_0 > 0σ0​>0, σϵ>0\sigma_\epsilon > 0σϵ​>0, pϵ∈[0,1]p_\epsilon \in [0,1]pϵ​∈[0,1], β≥0\beta \ge 0β≥0 are bundled in Params.Standing. "ϕ\phiϕ minimizes R~\widetilde{\mathcal R}R" is the predicate IsOptInteraction P φ: ϕ≥1\phi \ge 1ϕ≥1 and R~(ϕ)≤R~(ψ)\widetilde{\mathcal R}(\phi) \le \widetilde{\mathcal R}(\psi)R(ϕ)≤R(ψ) for all ψ≥1\psi \ge 1ψ≥1; there is no argmin function, so no junk value can satisfy the goal. Square roots are Real.sqrt, ϕ3/2\phi^{3/2}ϕ3/2 is ϕϕ\phi\sqrt\phiϕϕ​, and every statement restricts ϕ\phiϕ so that no radicand is negative and no denominator vanishes. Derivatives are stated with HasDerivAt and an explicit value. Rtilde P φ takes ϕ\phiϕ last, while the page writes both R~(ϕ,β)\widetilde{\mathcal R}(\phi,\beta)R(ϕ,β) and R~(β,ϕ)\widetilde{\mathcal R}(\beta,\phi)R(β,ϕ).

Two readings are fixed. The case "arg⁡min⁡=∞\arg\min = \inftyargmin=∞" is: no minimizer exists, R~\widetilde{\mathcal R}R is strictly decreasing on [1,∞)[1,\infty)[1,∞), and R~(ϕ)→0\widetilde{\mathcal R}(\phi) \to 0R(ϕ)→0. The comparative statics (5.6) are stated as monotone comparative statics: if a parameter increases (keeping pϵ≤1p_\epsilon \le 1pϵ​≤1), the minimizer moves weakly in the stated direction, and strictly whenever the original minimizer exceeds 111. The monotonicity clauses quantify over minimizers for both parameter sets, and the existence clause of the goal ensures both exist, so they are not vacuous. Stating the goal about fff alone, or defining ϕ0\phi_0ϕ0​ by sInf or by a formula, would trivialize the claim; the goal is about R~\widetilde{\mathcal R}R and its minimizers.

Part (i) of Proposition 5.1, which relates R\mathcal RR to R~\widetilde{\mathcal R}R with unquantified O(⋅)O(\cdot)O(⋅) error terms, is not formalized; neither is the optimal investment strategy of Proposition 4.1. The development needs one-variable real calculus from Mathlib, including square-root and quotient derivatives, monotonicity and convexity on intervals, and limits at infinity. Proofs of the milestones, of the convexity of ggg on all of [1,∞)[1,\infty)[1,∞) (which appears to hold without the hypothesis g(1)<0g(1) < 0g(1)<0), and of the derivative form of (5.6) on the interior region are all welcome.

Selected references

  • A. Capponi, S. Ólafsson, T. Zariphopoulou, Personalized Robo-Advising: Enhancing Investment through Client Interaction, Management Science 68(4), 2022; preprint arXiv:1911.01391v2 (the version cited for all page and equation numbers). https://arxiv.org/abs/1911.01391
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Dynamical SystemsGroup TheoryProbability·Captain: dbenbenn

Is the group IET of interval exchange transformations amenable?Open Problem

This mission formalizes the question whether the group IET\mathrm{IET}IET of interval exchange transformations is amenable, Question 1.6 of Juschenko, Matte Bon, Monod and de la Salle, Extensive amenability and an application to interval exchanges, Ergodic Theory Dynam. Systems 38 (2018) 195–219, p. 4 (doi:10.1017/etds.2016.32), together with the landmark results of the literature on the question.

Motivation

An interval exchange transformation cuts the circle R/Z\mathbf R/\mathbf ZR/Z into finitely many arcs and puts them back in a different order. These maps model the dynamics of polygonal billiards with rational angles, and since Katok–Stepin (1967) and Keane (1975) they have been a central object of ergodic theory. Under composition they form a group, IET\mathrm{IET}IET. Two questions about this group are open: whether it contains a non-abelian free subgroup (Katok's question), and whether it is amenable, that is, whether it carries a finitely additive, translation-invariant probability measure on all of its subsets. Amenability would answer Katok's question in the negative, since an amenable group has no non-abelian free subgroup.

Timeline.

  • 1967: Katok and Stepin first consider exchanges of three or more intervals (JMMS, p. 4).
  • 1975: Keane introduces interval exchange transformations systematically and the terminology (doi:10.1007/BF01236981).
  • 2009: Novak shows that cyclic subgroups of IET\mathrm{IET}IET are undistorted (doi:10.3934/jmd.2009.3.379).
  • 2013: Dahmani, Fujiwara and Guirardel show that two generic interval exchange transformations do not generate a free group (doi:10.4171/GGD/209).
  • 2013: Juschenko and Monod prove that the topological full group of every minimal Cantor system is amenable, which gives the first finitely generated infinite simple amenable groups (doi:10.4007/annals.2013.178.2.7). The technical core is the case X=ZX = \mathbf ZX=Z of the lamplighter question for the wobbling group below (Juschenko–de la Salle, p. 2).
  • 2013: de Cornulier's Bourbaki exposé records that “La question de la moyennabilité du groupe entier IET est ouverte” (p. 1064-04; published 2014, arXiv:2002.09342).
  • 2013: Juschenko, Nekrashevych and de la Salle prove that recurrent actions are extensively amenable (arXiv 2013; published 2016, doi:10.1007/s00222-016-0664-6).
  • 2013: Juschenko and de la Salle prove that the lamplighter action of the wobbling group of a recurrent metric space of bounded geometry, for instance Z\mathbf ZZ or Z2\mathbf Z^2Z2, is amenable, and that it is not when the space contains a Lipschitz injective image of the binary tree; the case Zd\mathbf Z^dZd, d≥3d \ge 3d≥3, is left open (arXiv 2013; published 2015, doi:10.36045/bbms/1432840864).
  • 2015: Juschenko, Matte Bon, Monod and de la Salle introduce extensive amenability of group actions, show that a subgroup of IET\mathrm{IET}IET is amenable if and only if its action on R/Z\mathbf R/\mathbf ZR/Z is extensively amenable, prove that every subgroup of rational rank at most 222 is amenable, and show that finitely supported random walks are Liouville in rank 111 and are not in rank at least 333 (arXiv 2015; published 2018, doi:10.1017/etds.2016.32).
  • 2017: Dahmani, Fujiwara and Guirardel prove that every finitely generated torsion-free solvable subgroup of IET\mathrm{IET}IET is virtually abelian (arXiv 2017; published 2020, doi:10.5802/afst.1641).
  • 2018: Garban shows that the action of the wobbling group of a bounded degree graph is diffuse-extensively amenable if and only if the graph is recurrent, and conjectures that W(Zd)↷ZdW(\mathbf Z^d) \curvearrowright \mathbf Z^dW(Zd)↷Zd is not extensively amenable for d≥3d \ge 3d≥3 (arXiv 2018; published 2020, doi:10.4171/GGD/567).
  • 2026: Guelman and Liousse record (p. 2) that “there is no known example of non amenable or torsion-free non virtually abelian finitely generated iet-group” (arXiv:2601.23054). The question remains open as of 2026.

Setting

Write R/Z\mathbf R/\mathbf ZR/Z for the circle (UnitAddCircle). A permutation ggg of R/Z\mathbf R/\mathbf ZR/Z is an interval exchange transformation (IntervalExchange.IsIntervalExchange g) when it is right-continuous, has finitely many points of discontinuity, and has finitely many angles g(x)−xg(x) - xg(x)−x. Equivalently, ggg cuts the circle into finitely many half-open arcs and translates each of them. The group IET\mathrm{IET}IET (IntervalExchange.IET) is the subgroup of permutations of R/Z\mathbf R/\mathbf ZR/Z that they generate; a milestone states that it consists of the interval exchange transformations themselves. For a subgroup G≤IETG \le \mathrm{IET}G≤IET, the angle group Λ(G)\Lambda(G)Λ(G) (angleGroup G) is the subgroup of R/Z\mathbf R/\mathbf ZR/Z generated by all angles of elements of GGG, and the rational rank rkQ\mathrm{rk}_{\mathbf Q}rkQ​ (rationalRank) of a subgroup of R/Z\mathbf R/\mathbf ZR/Z is the supremum of the ddd such that Zd\mathbf Z^dZd embeds in it. For a subgroup Λ\LambdaΛ of R/Z\mathbf R/\mathbf ZR/Z, IET(Λ)\mathrm{IET}(\Lambda)IET(Λ) (IETOf Λ) consists of the elements of IET\mathrm{IET}IET all of whose angles lie in Λ\LambdaΛ.

A mean on a set SSS is a function mmm from the subsets of SSS to [0,∞][0, \infty][0,∞] with m(∅)=0m(\emptyset) = 0m(∅)=0, m(A∪B)=m(A)+m(B)m(A \cup B) = m(A) + m(B)m(A∪B)=m(A)+m(B) for disjoint A,BA, BA,B, and m(S)=1m(S) = 1m(S)=1. A group GGG is amenable (Garrido.IsAmenable G) when it carries a mean with m(gA)=m(A)m(gA) = m(A)m(gA)=m(A) for all g∈Gg \in Gg∈G and A⊆GA \subseteq GA⊆G. An action of GGG on a set XXX is amenable (IsAmenableAction G X) when XXX carries a GGG-invariant mean, and extensively amenable (IsExtensivelyAmenable G X) when the finite subsets of XXX carry a GGG-invariant mean that, for each finite E0⊆XE_0 \subseteq XE0​⊆X, gives full weight to the finite sets containing E0E_0E0​.

The milestones use further notions, defined precisely in the definitions item and in their own statements:

  • A finitely supported probability measure μ\muμ on GGG drives the left random walk gn=hn⋯h1g_n = h_n \cdots h_1gn​=hn​⋯h1​; the inverted orbit of x0∈Xx_0 \in Xx0​∈X is On={x0,g1−1x0,…,gn−1x0}O_n = \{x_0, g_1^{-1}x_0, \dots, g_n^{-1}x_0\}On​={x0​,g1−1​x0​,…,gn−1​x0​}. The action is recurrent (IsRecurrentAction) when for every symmetric such μ\muμ and every x0x_0x0​, the induced walk gnx0g_n x_0gn​x0​ returns to x0x_0x0​ with probability 111.
  • For a functor FFF from finite sets with injections to amenable groups, F(X)F(X)F(X) (extend F X) is its extension to an arbitrary set XXX by direct limits, and an action of GGG on XXX gives the semidirect product F(X)⋊GF(X) \rtimes GF(X)⋊G (FunctorProduct F G X) acting on F(X)F(X)F(X). The lamplighter case is F(X)=(Z/2Z)(X)F(X) = (\mathbf Z/2\mathbf Z)^{(X)}F(X)=(Z/2Z)(X) (Lamplighter G X).
  • The wobbling group W(X)W(X)W(X) (wobbling X) of a metric space XXX consists of the permutations ggg of XXX with sup⁡xd(x,gx)<∞\sup_x d(x, gx) < \inftysupx​d(x,gx)<∞.

Formalization targets

Goal

IsAmenable(IET).\mathrm{IsAmenable}(\mathrm{IET}).IsAmenable(IET).

The question is open. A proof settles it positively and, through von Neumann's theorem, answers Katok's question in the negative; a disproof shows that IET\mathrm{IET}IET is not amenable.

Landmarks

The milestones are results from the literature, stated as their sources state them. From Juschenko–Matte Bon–Monod–de la Salle: IET\mathrm{IET}IET is a group (p. 4); Lemmas 2.1 and 2.2 on extensive amenability; Theorem 1.3 and Corollary 1.4, the functorial criterion; Proposition 5.3, that a subgroup of IET\mathrm{IET}IET is amenable if and only if its action on R/Z\mathbf R/\mathbf ZR/Z is extensively amenable; Proposition 4.1 and Lemma 4.3, the inverted-orbit reformulations; Theorem 4.2, recurrence implies extensive amenability; Lemma 5.2 and Theorems 5.1 and 1.9, amenability in rational rank at most 222; and Theorem 1.10, the Liouville dichotomy, with the steps of its proof: Lemma 5.10, Proposition 5.11 with Lemma 5.13 (realizing IET(Λ;Σ)\mathrm{IET}(\Lambda; \Sigma)IET(Λ;Σ) as the topological full group of a minimal subshift of polynomial complexity), and Matte Bon's theorem for virtually cyclic groups. The external results these proofs cite are milestones too: Kesten's criterion for a graph (Woess, Theorem 10.6), Lyons–Peres Theorem 2.17 on rough embeddings, Pólya's theorem (already proved on the platform as MarkovMixing.polya_recurrence), the Baldi–Lohoué–Peyrière comparison lemma, and Matte Bon's Theorem 1.2 on topological full groups of subshifts of slow complexity. From Juschenko–de la Salle: Theorem 1.4 on the wobbling group, with coarse embeddings defined by non-decreasing control functions.

Two further open statements

Garban's question, whether W(Zd)↷ZdW(\mathbf Z^d) \curvearrowright \mathbf Z^dW(Zd)↷Zd is extensively amenable for every ddd, and Question 1.11 of Juschenko–Matte Bon–Monod–de la Salle, whether a polynomially growing Schreier graph forces extensive amenability, are stated as open milestones. Each comes with a milestone stating that a positive answer implies the goal.

Significance

The result. A proof would make IET\mathrm{IET}IET a natural amenable group containing, by Juschenko–Monod and Juschenko–Matte Bon–Monod–de la Salle, finitely generated infinite simple amenable groups, and would answer Katok's question. A disproof would give the first non-amenable finitely generated group of interval exchange transformations; by Theorem 1.9 it would have rational rank at least 333.

Formalizing it. The definitions of extensive amenability, of the functorial semidirect products F(X)⋊GF(X) \rtimes GF(X)⋊G, of inverted orbits and recurrent actions, and of wobbling groups are reusable beyond this mission, as are the external probabilistic results (Kesten's criterion, rough embeddings and recurrence). Pólya's theorem is already formalized and proved on the platform (MarkovMixing.polya_recurrence). None of the other landmarks is formalized.

Difficulty

Every known amenability proof for subgroups of IET\mathrm{IET}IET passes through Proposition 5.3 and then needs extensive amenability of the action on the circle. The available criterion for extensive amenability is recurrence of the Schreier graphs, which embed into lattices Zd\mathbf Z^dZd with ddd the rational rank; for d≥3d \ge 3d≥3 these graphs can be transient, so recurrence is unavailable. Garban's theorem shows that the natural strengthening of extensive amenability fails for all transient wobbling actions, and Theorem 1.10 shows that the Liouville route fails in rank at least 333.

Formalization scope

R/Z\mathbf R/\mathbf ZR/Z is UnitAddCircle, and permutations act on it by evaluation. IET\mathrm{IET}IET is defined as the subgroup generated by the interval exchange transformations, so that its group structure needs no proof inside the definitions; a milestone states that nothing else lies in it. The source's precise definition (“a right-continuous permutation ggg of R/Z\mathbf R/\mathbf ZR/Z such that the set {gx−x,x∈R/Z}\{gx - x, x \in \mathbf R/\mathbf Z\}{gx−x,x∈R/Z}, called the set of angles of ggg, is finite”) is read together with its opening phrase, “cutting this circle into finitely many intervals”, so the definition also requires finitely many points of discontinuity: without that requirement a right-continuous permutation with two angles can have infinitely many discontinuities, and the cocycle of Proposition 5.3 would not be finitely supported. Means take values in [0,∞][0, \infty][0,∞] and are normalized to total mass 111. Random walks have finitely supported step distributions μ:G→0R\mu : G \to_0 \mathbf Rμ:G→0​R where the sources say “finitely supported”, and probabilities of events of a walk are finite sums over the step sequences. Recurrence of a Markov chain is return to the starting point with probability 111, expressed through first-return probabilities. Functors I→AmenI \to \mathrm{Amen}I→Amen are Mathlib functors from the wide subcategory of FintypeCat on the injective maps to GrpCat with amenable values, extended to a set XXX by the filtered colimit over its finite subsets.

The goal admits no trivializing reading: IET\mathrm{IET}IET contains the irrational rotations and the non-rotation exchanges, and Garrido.IsAmenable is the standard notion. The external milestones (Kesten, Lyons–Peres, Baldi–Lohoué–Peyrière) are cited results, stated in the form the sources apply; proofs of them are welcome contributions in their own right.

Selected references

  • K. Juschenko, N. Matte Bon, N. Monod and M. de la Salle, Extensive amenability and an application to interval exchanges, Ergodic Theory Dynam. Systems 38 (2018) 195–219, doi:10.1017/etds.2016.32, arXiv:1503.04977.
  • K. Juschenko and M. de la Salle, Invariant means for the wobbling group, Bull. Belg. Math. Soc. Simon Stevin 22 (2015) 281–290, doi:10.36045/bbms/1432840864.
  • K. Juschenko, V. Nekrashevych and M. de la Salle, Extensions of amenable groups by recurrent groupoids, Invent. Math. 206 (2016) 837–867, doi:10.1007/s00222-016-0664-6.
  • K. Juschenko and N. Monod, Cantor systems, piecewise translations and simple amenable groups, Ann. of Math. 178 (2013) 775–787, doi:10.4007/annals.2013.178.2.7.
  • C. Garban, Inverted orbits of exclusion processes, diffuse-extensive-amenability, and (non-?)amenability of the interval exchanges, Groups Geom. Dyn. 14 (2020) 871–897, doi:10.4171/GGD/567.
  • Y. de Cornulier, Groupes pleins-topologiques [d'après Matui, Juschenko, Monod, ...], Séminaire Bourbaki, exposé 1064, Astérisque 361 (2014) 183–223, arXiv:2002.09342.
  • F. Dahmani, K. Fujiwara and V. Guirardel, Free groups of interval exchange transformations are rare, Groups Geom. Dyn. 7 (2013) 883–910, doi:10.4171/GGD/209.
  • F. Dahmani, K. Fujiwara and V. Guirardel, Solvable groups of interval exchange transformations, Ann. Fac. Sci. Toulouse Math. 29 (2020) 595–618, doi:10.5802/afst.1641.
  • M. Keane, Interval exchange transformations, Math. Z. 141 (1975) 25–31, doi:10.1007/BF01236981.
  • C. F. Novak, Discontinuity-growth of interval-exchange maps, J. Mod. Dyn. 3 (2009) 379–405, doi:10.3934/jmd.2009.3.379.
  • R. Lyons and Y. Peres, Probability on Trees and Networks, Cambridge University Press, 2016, doi:10.1017/9781316672815.
  • W. Woess, Random Walks on Infinite Graphs and Groups, Cambridge University Press, 2000, doi:10.1017/CBO9780511470967.
  • N. Matte Bon, Subshifts with slow complexity and simple groups with the Liouville property, Geom. Funct. Anal. 24 (2014) 1637–1659, doi:10.1007/s00039-014-0293-4.
  • P. Baldi, N. Lohoué and J. Peyrière, Sur la classification des groupes récurrents, C. R. Acad. Sci. Paris Sér. A–B 285 (1977) A1103–A1104 (no DOI).
  • N. Guelman and I. Liousse, Some elementary amenable subgroups of interval exchange transformations, arXiv:2601.23054 (2026).
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Quantum Information·Captain: Goku

Distilling common randomness from bipartite quantum statesResearch Paper

Motivation

The problem of converting noisy quantum correlations between two parties into noiseless classical ones using a limited amount of one-way classical communication is addressed. A single-letter formula for the optimal trade-off between the extracted common randomness and classical communication rate is obtained for the special case of classical-quantum correlations. The resulting curve is intimately related to the quantum compression with classical side information trade-off curve Q∗(R)Q^*(R)Q∗(R) of Hayden, Jozsa and Winter. For a general initial state we obtain a similar result, with a single-letter formula, when we impose a tensor product restriction on the measurements performed by the sender; without this restriction the trade-off is given by the regularization of this function. Of particular interest is a quantity we call ``distillable common randomness'' of a state: the maximum overhead of the common randomness over the one-way classical communication if the latter is unbounded. It is an operational measure of (total) correlation in a quantum state. For classical-quantum correlations it is given by the Holevo mutual information of its associated ensemble, for pure states it is the entropy of entanglement. In general, it is given by an optimization problem over measurements and regularization; for the case of separable states we show that this can be single-letterized.

This mission is the statement-level formalization of Distilling common randomness from bipartite quantum states (arXiv:quant-ph/0304196v2). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

22 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Regularization of the one-way common-randomness trade-off (Abstract and §3: regularized one-way common-randomness trade-off, PDF p. 15). 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

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

  • Appendix (30): A valid conditional typical-projector extension with a restriction controlling all local subblock lengths and conditional frequency tolerances. (source-ambiguity)

Selected references

  • Distilling common randomness from bipartite quantum states, arXiv:quant-ph/0304196v2, https://arxiv.org/abs/quant-ph/0304196v2
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🏆Completed
Quantum Information·Captain: Goku

Fundamental Limits of Repeaterless Quantum CommunicationsResearch Paper

Motivation

Quantum communications promises reliable transmission of quantum information, efficient distribution of entanglement and generation of completely secure keys. For all these tasks, we need to determine the optimal point-to-point rates that are achievable by two remote parties at the ends of a quantum channel, without restrictions on their local operations and classical communication, which can be unlimited and two-way. These two-way assisted capacities represent the ultimate rates that are reachable without quantum repeaters. By constructing an upperbound based on the relative entropy of entanglement and devising a dimension-independent technique dubbed "teleportation stretching", we establish these capacities for many fundamental channels, namely bosonic lossy channels, quantum-limited amplifiers, dephasing and erasure channels in arbitrary dimension. In particular, we determine the fundamental rate-loss trade-off affecting any protocol of quantum key distribution. Our findings set the ultimate limits of point-to-point quantum communications and provide the most precise and general benchmarks for quantum repeaters.

This mission is the statement-level formalization of Fundamental Limits of Repeaterless Quantum Communications (arXiv:1510.08863v8). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

1 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Finite-dimensional teleportation covariance and the Choi commutator (Eqs.(79)–(80), PDF p. 14). 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

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

  • Main result: repeaterless pure-loss capacities, Eq.(19): Bosonic Hilbert space; Bosonic density operator; Bosonic CPTP channel; Pure-loss channel; LOCC protocol; Adaptive protocol; Protocol output; Private state; Achievable rate; Two-way capacity; Bipartite partial trace; Bosonic trace distance (hard)
  • Theorem 1 (general weak converse), Eq.(7): Quantum relative entropy; Relative entropy of entanglement; Regularized adaptive REE bound; Adaptive protocol; Protocol output; Two-way capacity; Private state; LOCC protocol; Bosonic density operator; Bipartite partial trace; Bosonic trace distance (hard)
  • Proposition 2 (tele-covariance): Teleportation covariance; Teleportation LOCC; Teleportation unitaries; Choi state; TMSV family; Asymptotic channel simulation; Exact channel simulation; Bipartite partial trace; Bosonic trace distance (hard)
  • Lemma 3 (Stretching), Eqs.(11)–(12): Adaptive protocol; Protocol output; LOCC protocol; Exact channel simulation; Asymptotic channel simulation; Tensor-power state; Choi state; Bipartite partial trace; Bosonic trace distance (hard)
  • Theorem 5 (one-shot REE bound), Eqs.(15)–(16): Asymptotic-resource REE comparator convergence class in Eq.(4) (source-ambiguity)
  • Finite-resource REE converse, Eqs.(13)–(15): Exact channel simulation; LOCC protocol; Protocol output; Relative entropy of entanglement; Regularized REE; Tensor-power state; Two-way capacity; Bipartite partial trace; Bosonic trace distance (hard)
  • Proposition 6, Eq.(31): Choi state; Exact channel simulation; Two-way capacity; Distillable key; Relative entropy of entanglement; Regularized REE; Channel REE; Private state; Bipartite partial trace; Bosonic trace distance (hard)
  • Theorem 7: Gaussian cross entropy and relative entropy, Eqs.(58)–(61): Gaussian state; Symplectic form; Covariance matrix; Gibbs matrix; Gaussian cross entropy; Quantum relative entropy; Bosonic von Neumann entropy; Bipartite partial trace; Bosonic trace distance (hard)
  • Lemma 8: energy truncation projector: Bosonic Hilbert space; Bosonic density operator; Total photon number; Energy-constrained state; Photon truncation projector; Postselected truncated state; Bosonic trace distance; Bipartite partial trace (hard)
  • Lemma 9: CPTP energy truncation: Energy-constrained state; Photon truncation projector; Truncation channel; Bosonic trace distance; Bosonic CPTP channel; Bipartite partial trace (hard)
  • Lemma 10: local CV–DV truncation and two classical bits: Mode-dependent local bosonic truncation error for arbitrary m_a,m_b (source-ambiguity)
  • Lemma 11 (Shield size; adapted from S14): Private state; Shield dimension; Adaptive protocol; Protocol output; Distillable key; One-way key-distillation protocol; LOCC protocol; Achievable rate; Bipartite partial trace; Bosonic trace distance (hard)
  • Operational task equivalences, p.2: Two-way capacity; Achievable rate; Private state; LOCC protocol; Adaptive protocol; Bipartite partial trace; Bosonic trace distance (hard)
  • Teleportation-covariant Gaussian, Pauli and erasure families: Teleportation covariance; Teleportation unitaries; Gaussian channel; Pauli channel; Erasure channel; Asymptotic channel simulation; Choi state; Bipartite partial trace; Bosonic trace distance (hard)
  • Every channel has an LOCC resource simulation: Exact channel simulation; Asymptotic channel simulation; Teleportation LOCC; Choi state; TMSV family; Bosonic CPTP channel; Bipartite partial trace; Bosonic trace distance (hard)
  • Capacities of distillable channels and one-way achievability: Asymptotic Choi REE and distillable-channel convention (source-ambiguity)
  • Fading-channel resource REE bound, Eq.(17): Asymptotic-resource REE in the fading expectation (source-ambiguity)
  • Two-way quantum communication, Eqs.(114)–(120): Asymptotic-resource entanglement flux for the two directional channels (source-ambiguity)
  • Multiband capacity bounds and additivity, Eqs.(121)–(128): Asymptotic-resource entanglement flux defining distillable bands (source-ambiguity)
  • High-loss rate-loss law, Eq.(20): Pure-loss channel; Two-way capacity (hard)
  • Strict two-way advantage of a lossy channel: Pure-loss channel; Two-way capacity; Unassisted quantum capacity (hard)
  • Lossy capacity equals distributed discord, Eq.(S128): Pure-loss channel; TMSV family; Choi state; Quantum discord; Gaussian discord; Two-way capacity; Bipartite partial trace; Bosonic trace distance (hard)
  • Pure-loss feedback and multiband operational specializations: Bidirectional protocol; Multiband channel; Pure-loss channel; Two-way capacity (hard)
  • Multimode fibre bandwidth formula, Eq.(21): Temporal-mode count relating physical bandwidth W to independent multiband channel uses (source-ambiguity)
  • Fading lossy-channel operational bound, Eq.(22): Fading channel; Publicly flagged mixture; Pure-loss channel; Two-way capacity (hard)
  • Lossy-component bound for composite channels: Composite channel; Pure-loss channel; Bosonic CPTP channel; Two-way capacity (hard)
  • Thermal-loss capacity sandwich, Eqs.(25),(S126): Thermal-loss channel; Thermal entropy; Two-way capacity; Coherent information (hard)
  • Thermal amplifier capacity sandwich, Eqs.(27),(S142): Thermal amplifier channel; Thermal entropy; Two-way capacity; Coherent information (hard)
  • Quantum-limited amplifier capacities, Eqs.(28),(S143): Thermal amplifier channel; Two-way capacity; Unassisted quantum capacity (hard)
  • Additive Gaussian noise capacity sandwich, Eqs.(30),(S147): Additive-noise channel; Two-way capacity; Coherent information (hard)
  • Gaussian entanglement-flux formulas, Eqs.(23),(26),(29), S124,S141,S146: Eq.(4) asymptotic-resource REE applied to the nonconvergent S119 comparator family (source-ambiguity)
  • Explicit Gaussian comparator relative-entropy limits, S123,S134,S140,S145: Gaussian separable comparator; TMSV family; Choi state; Gaussian cross entropy; Quantum relative entropy; Thermal-loss channel; Thermal amplifier channel; Additive-noise channel; Thermal entropy; Bipartite partial trace; Bosonic trace distance (hard)
  • Secondary canonical Gaussian forms: Eq.(4) entanglement flux of secondary bosonic canonical forms (source-ambiguity)
  • Finite input/output dimensionality bound: Two-way capacity; Exact channel simulation; Teleportation LOCC (hard)
  • Qubit Pauli flux and capacity bounds, Eqs.(33)–(34), S173–S176: Pauli channel; Choi state; Shannon entropy; Relative entropy of entanglement; Two-way capacity; Coherent information; Bipartite partial trace; Bosonic trace distance (hard)
  • Qudit Pauli bounds, Eqs.(S190)–(S191): Pauli channel; Teleportation unitaries; Choi state; Shannon entropy; Relative entropy of entanglement; Two-way capacity; Gaussian-free separable comparator; Bipartite partial trace; Bosonic trace distance (hard)
  • Depolarizing channels in arbitrary dimension, Eqs.(36)–(37), S196–S198: Depolarizing channel; Choi state; Relative entropy of entanglement; Shannon entropy; Two-way capacity; Bipartite partial trace; Bosonic trace distance (hard)
  • Dephasing capacities in arbitrary dimension, Eqs.(39),(41), S182,S204: Dephasing channel; Teleportation unitaries; Choi state; Shannon entropy; Relative entropy of entanglement; Two-way capacity; Unassisted quantum capacity; Bipartite partial trace; Bosonic trace distance (hard)
  • Secret-key capacity of a qudit erasure channel, Eqs.(43)–(44), S166–S167: Erasure channel; Choi state; Two-way capacity; Relative entropy of entanglement; One-way entanglement-distillation protocol; Bipartite partial trace; Bosonic trace distance (hard)
  • Amplitude damping simulation through a bosonic loss channel, Eqs.(46), S208–S209: Amplitude damping channel; Single-rail encoding; Pure-loss channel; Asymptotic channel simulation; Protocol output; Teleportation covariance; Bipartite partial trace; Bosonic trace distance (hard)
  • Amplitude damping capacity sandwich from loss, Eqs.(47)–(48), S214: Amplitude damping channel; Two-way capacity; Coherent information (hard)
  • Amplitude damping strict advantage over unassisted capacity: Amplitude damping channel; Coherent information; Unassisted quantum capacity; Two-way capacity (hard)
  • Amplitude damping variational squashing bounds, S231,S233–S234: Amplitude damping channel; Squashed entanglement; Squashing dilation; Entanglement-assisted classical capacity; Two-way capacity (hard)
  • Claimed closed amplitude damping bound, Eq.(49), S232,S235: A valid optimizer or repaired proof for the closed S232/S235 squashing bound (source-ambiguity)
  • Hashing inequality for energy-bounded bosonic states: Energy-constrained state; Bosonic von Neumann entropy; Coherent information; Distillable entanglement; One-way entanglement-distillation protocol; Photon truncation projector; Bipartite partial trace; Bosonic trace distance (hard)
  • Claimed monotonic and finite Gaussian information limits, S108–S112: Valid parameter domain and direction/finite-limit assertion for Gaussian coherent information (source-ambiguity)
  • Finite-error key bound, Eqs.(S82)–(S83): Private state; Untwisting map; Relative entropy distance to untwisted separable states; Relative entropy of entanglement; Protocol output; Bosonic trace distance; Bipartite partial trace (hard)
  • Energy-constrained loss lower and upper bounds, S247: Pure-loss channel; TMSV family; Thermal entropy; Energy-constrained capacity; Coherent information; Two-way capacity (hard)
  • Claimed optimal loss protocol CC cost, S250–S251: Quantized source coding convention turning continuous heterodyne entropy into a bit cost (source-ambiguity)
  • Claimed finite-energy CV Bell POVM, Eq.(70): Normalized finite-energy joint Bell POVM under the stated displacement measure (source-ambiguity)
  • Claimed optimal fixed-marginal separable Gaussian comparator: Exact optimization domain of the asserted fixed-marginal Gaussian comparator optimality (source-ambiguity)
  • Finite-energy adaptive simulation error, Eqs.(98)–(106): Energy-constrained diamond norm; Energy-constrained state; Adaptive protocol; Protocol output; Asymptotic channel simulation; Bosonic trace distance (hard)

Selected references

  • Fundamental Limits of Repeaterless Quantum Communications, arXiv:1510.08863v8, https://arxiv.org/abs/1510.08863v8
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Lie-Wedge Stratification and Pure-State Stabilizability in Single-Channel Qubit ControlResearch Paper

Motivation

We ask when qubit controls can produce an effective generator that drives every initial state to the same pure state. Lie-algebra closure alone cannot answer this question because it loses the distinction between reversible control and irreversible dissipation. Lie wedges retain this distinction by enforcing nonnegative strengths for dissipative generators. For drift-free qubits with Hamiltonian controls available with either sign and at most one independently actuated dissipator generated by a traceless jump operator, we classify all nontrivial systems into thirteen structural types, or strata. Explicit tests assign each system to a stratum, and necessary and sufficient conditions determine whether its Lie wedge contains a stabilizing generator. These criteria distinguish stabilizable and non-stabilizable systems even when they share the same generated Lie algebra and stratum. In one exceptional stratum, a single dissipative orientation cannot stabilize a pure state even with the available Hamiltonian controls. Averaging two orientations of the same dissipative channel, related by those controls, produces a stabilizing generator. △ Less

This mission is the statement-level formalization of Lie-Wedge Stratification and Pure-State Stabilizability in Single-Channel Qubit Control (arXiv:2610.00046v1). 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 Lemma 2.7: Dissipation functional with basis normalization (Lemma 2.7, 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

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

  • Theorem 2.3: Affine structure of the Lindblad–Kossakowski algebra: cited background result outside the original-result drafting scope (hard)
  • Theorem 2.4: GKLS characterization in Kossakowski form: cited background result outside the original-result drafting scope (hard)
  • Lemma 2.5: Hamiltonian edge of the GKLS wedge: cited background result outside the original-result drafting scope (hard)
  • Theorem 2.6: The GKLS cone is a Lie wedge: cited background result outside the original-result drafting scope (hard)
  • Corollary 2.8: Hamiltonian rigidity of the commutator ideal: computed derived ideal, solvable radical, and Levi projection inside the real GKLS algebra (hard)
  • Proposition 2.15: Finite iterative construction of the minimal closed Lie wedge: minimal closed Lie wedge, edge-generated exponential subgroup, and tangent semigroup (hard)
  • Lemma 2.17: Radical slice is a Lie wedge: cited background result outside the original-result drafting scope (hard)
  • Lemma 2.18: Quotient cone and projected-edge invariance: cited background result outside the original-result drafting scope (hard)
  • Lemma 2.19: Fiber-map properties: cited background result outside the original-result drafting scope (hard)
  • Proposition 2.20: Necessity of fiber compatibility: cited background result outside the original-result drafting scope (hard)
  • Proposition 2.22: Unique reconstruction from admissible fiber data: cited background result outside the original-result drafting scope (hard)
  • Theorem 2.23: Levi decomposition–reconstruction correspondence: cited background result outside the original-result drafting scope (hard)
  • Lemma 3.4: Invariance under the allowed equivalences: computed Levi-data tuple and transported minimal wedge under specification equivalences (hard)
  • Lemma 3.9: Edge rigidity including several channels and one-sided drift: minimal Lie wedge for general finite multi-channel specifications with one-sided Hamiltonian drifts (hard)
  • Proposition 3.10: Four possible semisimple Levi factors: solvable radical quotient and real Lie isomorphism classes of Levi complements (hard)
  • Lemma 3.11: Orbit-average representation of the wedge: compact control group, finite Borel orbit measures, and minimal/radical Lie wedges (hard)
  • Corollary 3.12: Full-control quadrupole-free radical cone: quadrupole-free SO(3) orbit-average cone and its radical span (hard)
  • Corollary 3.13: Sharp axial circular radical cone: axial orbit Fourier moments and exact circular radical cone (hard)
  • Lemma 3.14: Magic locus for a nonzero radical wedge: uniform axial channel average and actual radical-wedge intersection (hard)
  • Corollary 3.16: Axial Lie-closure dichotomy: a source-pinned choice between traceless input and full symmetric input (source-ambiguity)
  • Lemma 3.18: Parametric matrix projections and translation kernels: independent Table 1 row predicates plus computed matrix projections and translation kernels (hard)
  • Corollary 3.19: Radicals across the nontrivial channel strata: Table 1 row predicates, computed solvable radicals, and the affine weight-zero average (hard)
  • Corollary 3.20: Radical cones across the nontrivial channel strata: Table 1 row predicates and computed radical cones from orbit averages (hard)
  • Theorem 3.21: Exhaustive thirteen-value classification and residual moduli: full thirteen-row discriminant assignment, computed Levi tuple, and residual orbit-moduli quotient (hard)
  • Corollary 3.23: Globality and the exact semialgebra boundary: closed switched semigroup tangent wedge and local BCH-closed Lie semialgebra predicate (hard)
  • Lemma 3.25: Pure candidates and uniform dissipative contraction: normalized pure stationary states of finite orbit-average generators and almost-everywhere jump eigenstate compatibility (hard)
  • Theorem 3.26: Axial stabilization iff the scalar criterion, with minimum support: trace-norm pure-state global asymptotic stability in the computed axial wedge and minimum distinct orbit-ray support (hard)
  • Corollary 3.27: Thirteen-stratum pure-state stabilization atlas: all Table 2 capability predicates and minimum support over independently defined thirteen strata (hard)
  • Remark 2.12 and the strict-inclusion example: minimal local wedge, closed autonomous semigroup, and quasi-periodic Hamiltonian witness (hard)
  • Unnumbered endpoint stabilization result: pure-state GAS for the actual wedge at q=0 and bare damping at q=1 (hard)
  • Remark 3.29: full-control pure targets: orbit-ray pure-target GAS and laboratory-fixed-dissipator comparison (hard)
  • §3.8: all four Levi types are realized: actual Levi-type predicates and realized row assignment (hard)
  • §4: the mixed reductive Q4 wedge does not split: computed Q4 minimal wedge and dimensions of its span versus edge/average span (hard)

Selected references

  • Lie-Wedge Stratification and Pure-State Stabilizability in Single-Channel Qubit Control, arXiv:2610.00046v1, https://arxiv.org/abs/2610.00046v1
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All coherent measurements provide observational ergotropic advantageResearch Paper

Motivation

The use of quantum resources in the work extraction from a quantum system is an emerging research topic. Recently, [arXiv:2602.22893] established the necessity of measurement coherence for obtaining advantage in work extraction from an unknown isolated quantum system. However, a quantitative relation between the magnitude of this advantage and established measures of measurement coherence is missing. Here, we establish such a connection by introducing a faithful operational quantifier of the work advantage provided by a measurement. We show that measurement coherence is necessary and sufficient for a positive advantage, and derive upper and lower bounds in terms of the robustness of measurement coherence and an l∞l_{\infty}l∞​ norm based coherence measure respectively. Finally, we examine this quantifier of advantage from the resource theoretic perspective. Our results provide an operational characterisation of measurement coherence as a resource for work extraction and reveal a nontrivial relation between its resource content and thermodynamic value. △ Less

This mission is the statement-level formalization of All coherent measurements provide observational ergotropic advantage (arXiv:2609.18735v1). 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 Theorem 1 (Theorem 1, 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

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

  • Appendix A closing sentence: A quantified meaning of optimality for the final Theorem 3 coefficient: optimal for each fixed dimension, or a weaker assertion that the displayed dimension-dependent bound cannot be improved uniformly. (source-ambiguity)

Selected references

  • All coherent measurements provide observational ergotropic advantage, arXiv:2609.18735v1, https://arxiv.org/abs/2609.18735v1
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Coherence-assisted quantum state preparation and thermal control through repeated interactionsResearch Paper

Motivation

We investigate the relaxation dynamics and steady state of a qubit interacting with a coherent environment through an energy-conserving flip-flop interaction within the Markovian repeated-interaction framework. We derive an exact analytical solution for the evolving and stationary state, nonperturbative in the environmental coherence. We show that environmental coherence provides a resource for dissipative state preparation by expanding the set of accessible steady states. In particular, coherent ancillas can increase the system ground- state population beyond that of the bath, corresponding to an effective temperature below the bath temperature, and enhance its steady-state purity, with these effects controlled by the interplay between the system energy scale and the system-ancilla coupling. Nevertheless, we prove that the purity of the system can never exceed the purity of the ancilla. We further analyze the thermodynamics of the protocol and show that environmental coherence can modify and even reverse the natural direction of heat transfer, giving rise to anomalous heat flow. Remarkably, for fixed interaction parameters, the direction of the coherence-induced heat transfer is governed by the relative phase between the system and ancilla coherence, whereas their magnitudes determine the amount of heat exchanged. Our results establish environmental coherence as a resource for controlling steady-state preparation and energy transfer in repeated-interaction dynamics. △ Less

This mission is the statement-level formalization of Coherence-assisted quantum state preparation and thermal control through repeated interactions (arXiv:2610.10794v1). 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 Stationary purity is capped by ancilla purity (Abstract; §III B Eq.(26); Appendix D: ancilla purity cap, PDF p. 19). 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

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

  • §II B: K>0 claimed to suffice for relaxation: A correct complete relaxation domain replacing K>0 alone (source-ambiguity)
  • §III A: alleged cooling-only behavior at odd pi collisions: An attracting state at odd-pi collisions (source-ambiguity)
  • §III A: maximum percentage and doubled-polarization claims: Consistent optimization claim and physically admissible nonzero polarization doubling (source-ambiguity)
  • Appendix A.2: claimed equivalence of unitary and Hamiltonian symmetry: A valid converse from fixed-duration unitary symmetry to Hamiltonian symmetry (source-ambiguity)
  • Appendix B Eqs.(B4)–(B7): claimed continuous-time master equation: A consistent collision-limit scaling, coherence scaling and rotating frame (source-ambiguity)
  • Appendix E: literal unrounded real upper bound: An integer upper bound for a strict trace-distance tolerance (source-ambiguity)
  • Appendix E Fig.9: observed coherence-induced relaxation slowdown: Quantified parameter domain and comparison for actual collision counts (source-ambiguity)

Selected references

  • Coherence-assisted quantum state preparation and thermal control through repeated interactions, arXiv:2610.10794v1, https://arxiv.org/abs/2610.10794v1
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The Minimal Dimension of Entangled-Noise AdvantageResearch Paper

Motivation

Can entangled noise erase entanglement more efficiently than separable noise? Standard robustness restricts the added noise to separable states; generalized robustness allows any state. We prove that the two costs coincide for every two-qubit state and give an explicit full-rank qubit--qutrit state with a strict gap. Positivity under partial transpose (PPT) characterizes separability in both dimensions, so the boundary is not caused by a failure of the PPT criterion. Instead, product-vector geometry permits a rank-one bridge between the two-qubit dual optimizations and supplies a two-dimensional completely entangled subspace for the qubit--qutrit separation. Local isometric embeddings complete the finite-dimensional bipartite classification, also for any fixed multipartite cut. Combined with known three-qubit separation, the result classifies universal equality relative to full separability in all finite multipartite systems. △ Less

This mission is the statement-level formalization of The Minimal Dimension of Entangled-Noise Advantage (arXiv:2609.28367v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

45 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Main-text Theorem 1; seed announced in abstract (Main-text Theorem 1; seed announced in abstract, 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.

Selected references

  • The Minimal Dimension of Entangled-Noise Advantage, arXiv:2609.28367v1, https://arxiv.org/abs/2609.28367v1
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Optimal entanglement criteria from trace invariantsResearch Paper

Motivation

Randomized measurement protocols give experimental access to low-degree polynomial invariants of a quantum state rather than to the state itself, which raises the question of what the best entanglement criterion is that can be built from finitely many such invariants. In this work we answer this question through convex duality. For each degree we introduce the cone of local unitary trace inequalities that are valid for separable bipartite states in all local dimensions, together with its one-matrix counterparts for Hermitian and positive semidefinite matrices. Each cone is the polar dual of a moment cone; we also determine the minimal combinatorial parametrization of the separable cone. The framework organizes the known moment criteria: the PPT criterion using the first three moments of the partial transposition is the image under an embedding of a Hankel determinant from the positive semidefinite cone to the bipartite cone, which we show to be an extremal ray, and we determine the first nontrivial separable cone completely, finding exactly four extremal rays. The framework allows us to analyze the realignment criterion and its centered (or enhanced) variant. We prove that the even singular value moments of the (centered) realignment matrix are trace invariants, associated with explicit fixed-point-free involutions. Extracting the optimal trace-norm bound from mmm such moments thus becomes a dimension-free truncated moment problem, which we solve in closed form for m=2m = 2m=2 and relax to a semidefinite program of size O(m)O(m)O(m) for arbitrary mmm. The dual solutions are polynomial minorants of x\sqrt{x}x​ on [0,1][0,1][0,1], and two explicit families, binomial and L1L^1L1-weighted, yield hierarchies of separability inequalities. Finally, we compare the criteria against one another and on PPT entangled states. △ Less

This mission is the statement-level formalization of Optimal entanglement criteria from trace invariants (arXiv:2609.29471v1). Every numbered result of the paper was scanned. The results stated here are open sorry goals, ready for solvers to prove.

What is formalized

43 statements of the paper are in Lean 4 (Mathlib 0df444a). The goal theorem is Abstract / §4.1: separable trace inequalities and their moment polar (Abstract / §4.1: separable trace inequalities and their moment polar, 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:

  • Abstract / Introduction unnumbered: claimed pointwise convergence of weighted minorants: Abstract / Introduction unnumbered: claimed pointwise convergence of weighted minorants (source-ambiguity)
  • §6.4 / Table 1: noisy Tiles numerical detection benchmark: §6.4 / Table 1: noisy Tiles numerical detection benchmark (source-ambiguity)
  • Table 2: rounded noisy binomial thresholds: Table 2: rounded noisy binomial thresholds (source-ambiguity)
  • Appendix A Eq.(48): approximate degree-five optimizer: Appendix A Eq.(48): approximate degree-five optimizer (source-ambiguity)

Selected references

  • Optimal entanglement criteria from trace invariants, arXiv:2609.29471v1, https://arxiv.org/abs/2609.29471v1
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