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Thomson N=7N=7N=7: the cap certificate satisfies the cap specification at a0=−99100a_0=-\tfrac{99}{100}a0​=−10099​

Proved
ThomsonN7.Final.capspec_cap

by Lucas · Oct 10, 2026 · Mathlib 0df444a (Lean v4.33.1)

discrete-geometrythomson-problem

Let φ(t)=(2−2t)−1/2\varphi(t)=(2-2t)^{-1/2}φ(t)=(2−2t)−1/2, let PPP be the pentagonal bipyramid and EEE the Coulomb energy, and write c1=cos⁡2π5c_1=\cos\tfrac{2\pi}5c1​=cos52π​, c2=cos⁡4π5c_2=\cos\tfrac{4\pi}5c2​=cos54π​. The cap specification at a0=−99100a_0=-\tfrac{99}{100}a0​=−10099​ holds: there are reals e,δ,τe,\delta,\taue,δ,τ and functions HA,HB,HC:R→RH_A,H_B,H_C:\mathbb R\to\mathbb RHA​,HB​,HC​:R→R such that

  1. τ≤1165000\tau\le\tfrac1{165000}τ≤1650001​ and E(P)≤e+δE(P)\le e+\deltaE(P)≤e+δ;
  2. for every configuration yyy of seven distinct unit vectors in R3\mathbb R^3R3 in which the pair (0,1)(0,1)(0,1) realises the smallest inner product and ⟨y0,y1⟩≤a0\langle y_0,y_1\rangle\le a_0⟨y0​,y1​⟩≤a0​,
e ≤ ∑i<jHcls(i,j)(⟨yi,yj⟩),e\ \le\ \sum_{i<j}H_{\mathrm{cls}(i,j)}(\langle y_i,y_j\rangle),e ≤ i<j∑​Hcls(i,j)​(⟨yi​,yj​⟩),

where cls(i,j)\mathrm{cls}(i,j)cls(i,j) is AAA for the pair {0,1}\{0,1\}{0,1}, BBB for pairs meeting {0,1}\{0,1\}{0,1} in one point, and CCC otherwise; 3. HA≤φH_A\le\varphiHA​≤φ on [−1,a0][-1,a_0][−1,a0​] and φ(t)−HA(t)≤δ⇒∣t+1∣≤τ\varphi(t)-H_A(t)\le\delta\Rightarrow|t+1|\le\tauφ(t)−HA​(t)≤δ⇒∣t+1∣≤τ there; 4. HB≤φH_B\le\varphiHB​≤φ on [−1,1)[-1,1)[−1,1) and φ(t)−HB(t)≤δ⇒∣t∣≤τ\varphi(t)-H_B(t)\le\delta\Rightarrow|t|\le\tauφ(t)−HB​(t)≤δ⇒∣t∣≤τ there; 5. HC≤φH_C\le\varphiHC​≤φ on [−1,1)[-1,1)[−1,1) and φ(t)−HC(t)≤δ⇒∣t−c1∣≤τ\varphi(t)-H_C(t)\le\delta\Rightarrow|t-c_1|\le\tauφ(t)−HC​(t)≤δ⇒∣t−c1​∣≤τ or ∣t−c2∣≤τ|t-c_2|\le\tau∣t−c2​∣≤τ there.

This is the certificate half of the cap cell in the proof of the Thomson problem for seven electrons: combined with the soundness theorem ThomsonN7.Glue.capSpec_sound it gives E(P)≤E(y)E(P)\le E(y)E(P)≤E(y) on the cap.

Formalization Note Glue.CapSpec and the data of the certificate tc_cap are the platform definitions ThomsonN7_core and ThomsonN7_cap_data_1/2, taken verbatim from the source.

Preamble
import Definitions.Def_ThomsonN7_core
import Definitions.Def_ThomsonN7_cap_data_2
Formal statement
namespace ThomsonN7

theorem Final.capspec_cap : Glue.CapSpec (-99 / 100 : ℝ) := by sorry

end ThomsonN7
Source
H. Tran, Thomson problem N = 7 Lean proof package, https://github.com/huwngtran/thomson-n7-lean @ 25f2fa53119273458cfbb3c4230904bffdd61e53: paper/PAPER.md §7.2; Lean `ThomsonN7.Final.capspec_cap`, https://github.com/huwngtran/thomson-n7-lean/blob/25f2fa53119273458cfbb3c4230904bffdd61e53/formal/lean/ThomsonN7/Solution.lean#L16169; definition of `CapSpec` at https://github.com/huwngtran/thomson-n7-lean/blob/25f2fa53119273458cfbb3c4230904bffdd61e53/formal/lean/ThomsonN7/Solution.lean#L12717

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