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Average sensitivity of polynomial threshold functions is at most 3.762 d sqrt(n)

Proved
AverageSensitivity.polynomial_bound_3762_general

by Yuxuan Xu · Oct 16, 2026 · Mathlib 0df444a (Lean v4.33.1)

average-sensitivity-3762boolean-functionsinequalities

For all positive integers n,d, let p be any real polynomial in n variables with total degree at most d. On the uniform cube {-1,1}^n, define f(x)=1 when p(x)>=0 and f(x)=-1 otherwise. Let average sensitivity be the sum over coordinates of the probability that flipping that coordinate changes f. Then

AS⁡(f)≤1881500dn.\operatorname{AS}(f)\le\frac{1881}{500}d\sqrt n.AS(f)≤5001881​dn​.

The theorem includes zeros of p under the positive-at-zero convention and arbitrary polynomials, with no multilinearity assumption. There is no restriction d<=n. The weighted-grading construction is due to OpenAI; the refined coupling estimate is due to Lagdive, Aglave and Damre. This result formalizes their integration and extracts the sufficient coefficient 3.762; optimality is not asserted.

Preamble
import Mathlib
import Definitions.Def_GotsmanLinial
open OAI.LeanBlast.GotsmanLinial
open scoped BigOperators
Formal statement
theorem AverageSensitivity.polynomial_bound_3762_general {n d : ℕ} (hn : 1≤n) (hd : 1≤d)
    (p : MvPolynomial (Fin n) ℝ) (hdegree : p.totalDegree≤d) :
    averageSensitivity (polynomialThreshold p) ≤ (1881/500:ℝ)*(d:ℝ)*Real.sqrt (n:ℝ) := by sorry
Source
https://github.com/Anchen0823/average-sensitivity-lean/blob/b2e634415548e050c115f6f12732d8b6b4a5d27f/AverageSensitivity/Multilinearization.lean
Human review
  • Endorsed by Shuze Chen · Oct 16, 2026

    Confirmed by the moderator at approval.

  • Endorsed by Yuxuan Xu · Oct 16, 2026

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

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