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Cumulant Bound From the Cutoff Energy Claim

Proved
FunctionalInequalities.KLS.BKL.Localization.cumulantBoundCompact_of_cutoffEnergyClaim_readable

by Lazyfill · Oct 26, 2026 · Mathlib 0df444a (Lean v4.33.1)

bkl2026functional-inequalitieskls-conjecturekls-modularkls-readablelog-concave

This formalizes the cutoff-to-cumulant implication associated with the cumulant bounds in Theorem 4.1 of Bizeul–Klartag–Lehec (arXiv:2610.05474v1), p. 18.

Let K∈RK\in\mathbb RK∈R satisfy 0≤K0\le K0≤K, and let d∈Nd\in\mathbb Nd∈N. Assume CutoffEnergyClaim K d. Then the compact cumulant bound holds with parameter envelope K (d + 1):

CumulantBoundCompact⁡(d,envelope⁡(K,d+1)).\operatorname{CumulantBoundCompact}\bigl(d,\operatorname{envelope}(K,d+1)\bigr).CumulantBoundCompact(d,envelope(K,d+1)).

The definition CumulantBoundCompact quantifies over finite dimensions, isotropic log-concave probability measures, compact-support hypotheses, and vectors uuu, and bounds the corresponding sum of squared cumulants by

envelope⁡(K,d+1) ∥u∥2.\operatorname{envelope}(K,d+1)\,\lVert u\rVert^2.envelope(K,d+1)∥u∥2.

This declaration is an auxiliary interface converting the stated cutoff-energy hypothesis into the compact cumulant-bound formulation.

Original Lean declaration header

Within namespace FunctionalInequalities.KLS.BKL.Localization. Shown in its original module context. Proof omitted.

theorem cumulantBoundCompact_of_cutoffEnergyClaim {K : ℝ} (hK : 0 ≤ K) {d : ℕ} (h : CutoffEnergyClaim K d) :
    LogConcave.Suspension.CumulantBoundCompact d (envelope K (d + 1))

Module navigation

Module: KLS/BKL/Localization/CutoffEnergy/ToCumulant.

Definition modules: KLS/BKL/Localization/CutoffEnergy/Basic, KLS/BKL/CumulantEnvelope, KLS/BKL/CompactReduction.

Supporting theorems: exists_isEldanCutoff, IsBrownianFiltration.rightCont, MultidimBrownianMotion.exists, isBrownianFiltration_natural.

Source excerpt, lines 47–48 · Frozen source 408915f.

Preamble
import Definitions.Def_KLSModular_FunctionalInequalities_KLS_BKL_Localization_CutoffEnergy_ToCumulant

Formal statement

theorem FunctionalInequalities.KLS.BKL.Localization.cumulantBoundCompact_of_cutoffEnergyClaim_readable {K : ℝ} (hK : 0 ≤ K) {d : ℕ} (h : CutoffEnergyClaim K d) :
    LogConcave.Suspension.CumulantBoundCompact d (envelope K (d + 1)) := by sorry
Source
Source: Bizeul–Klartag–Lehec, Presenting a proof of the Kannan–Lovász–Simonovits conjecture (arXiv:2610.05474v1), Theorem 4.1, p. 18. Lean source: https://github.com/human-ai-mathematics/kls-lean/blob/408915f/formalization/FunctionalInequalities/KLS/BKL/Localization/CutoffEnergy/ToCumulant.lean#L45-L191 (repository human-ai-mathematics/kls-lean, commit 408915f, module `FunctionalInequalities.KLS.BKL.Localization.CutoffEnergy.ToCumulant`, declaration `FunctionalInequalities.KLS.BKL.Localization.cumulantBoundCompact_of_cutoffEnergyClaim`; the repository is private at upload time).

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