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Asymptotic sensitivity separation exponent

Definition
SensitivityCampaign

by marwahaha · Oct 15, 2026 · Mathlib 0df444a (Lean v4.33.1)

block-sensitivityboolean-functionssensitivity

An exponent a is achievable if, for every positive epsilon and every integer sensitivity threshold S ≥ 2, there is a total Boolean function f with s(f) ≥ S and bs(f) ≥ s(f)^(a−epsilon). The witnesses may depend on epsilon and S.

Definition code
import Mathlib
import Definitions.Def_SensitivitySeparation

namespace SensitivityCampaign

def AchievesExponent (a : ℝ) : Prop :=
  ∀ ε : ℝ, 0 < ε → ∀ S : ℕ, 2 ≤ S →
    ∃ (n : ℕ) (f : (Fin n → Bool) → Bool),
      S ≤ OAI.Paper320.sensitivity f ∧
      (OAI.Paper320.sensitivity f : ℝ) ^ (a - ε) ≤
        (OAI.Paper320.blockSensitivity f : ℝ)

end SensitivityCampaign
Source
https://github.com/bigospeedrun/site/issues/2
Read-back

What the Lean code literally says, in plain math · Codex (independent auditor sub-agent)

For a Boolean function ggg on mmm bits, let s(g)s(g)s(g) be the maximum, over all inputs, of the number of individual coordinates whose flip changes its output, and let b(g,y)b(g,y)b(g,y) be the maximum size of a family of pairwise disjoint nonempty coordinate sets whose separate flips at input yyy each change its output; the empty family is permitted and has size zero. Write b(g)b(g)b(g) for the maximum of b(g,y)b(g,y)b(g,y) over all inputs yyy. For any real number aaa, the proposition defined here holds exactly when, for every real ε>0ε>0ε>0 and every natural number S≥2S≥2S≥2, there exist a natural number mmm and a Boolean function ggg on mmm bits with S≤s(g)S≤s(g)S≤s(g) and s(g)a−ε≤b(g)s(g)^{a-ε}≤b(g)s(g)a−ε≤b(g), where sensitivity values are regarded as real numbers in this inequality. No sign restriction is imposed on aaa or a−εa-εa−ε. The function and dimension may depend on both εεε and SSS. The dimension is quantified over all natural numbers, including zero, but zero-dimensional functions have sensitivity zero and therefore cannot satisfy the required lower bound.

Human review
  • Endorsed by marwahaha · Oct 15, 2026

    Confirmed by the moderator at approval.

  • Endorsed by Shuze Chen · Oct 16, 2026

    Confirmed by the moderator at approval.

  • Endorsed by Leo Shaposhnik · Oct 16, 2026

    Confirmed by the mission captain (proposal self-audit).

  • Endorsed by @bwdaugherty · Oct 16, 2026

    Confirmed by the mission captain (proposal self-audit).

  • Endorsed by abhishekdpseok · Oct 16, 2026

    Confirmed by the mission captain (proposal self-audit).

  • Endorsed by Robin Kothari · Oct 16, 2026

    Confirmed by the mission captain (proposal self-audit).

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