English

Log concavity and concentration of Lipschitz functions on the Boolean hypercube

Probability 2020-07-28 v1 Combinatorics Functional Analysis

Abstract

It is well-known that measures whose density is the form eVe^{-V} where VV is a uniformly convex potential on \RRn\RR^n attain strong concentration properties. In search of a notion of log-concavity on the discrete hypercube, we consider measures on {1,1}n\{-1,1\}^n whose multi-linear extension ff satisfies log2f(x)β\Id\log \nabla^2 f(x) \preceq \beta \Id, for β0\beta \geq 0, which we refer to as β\beta-semi-log-concave. We prove that these measures satisfy a nontrivial concentration bound, namely, any Hamming Lipchitz test function φ\varphi satisfies \Varν[φ]n2Cβ\Var_\nu[\varphi] \leq n^{2-C_\beta} for Cβ>0C_\beta>0. As a corollary, we prove a concentration bound for measures which exhibit the so-called Rayleigh property. Namely, we show that for measures such that under any external field (or exponential tilt), the correlation between any two coordinates is non-positive, Hamming-Lipschitz functions admit nontrivial concentration.

Keywords

Cite

@article{arxiv.2007.13108,
  title  = {Log concavity and concentration of Lipschitz functions on the Boolean hypercube},
  author = {Ronen Eldan and Omer Shamir},
  journal= {arXiv preprint arXiv:2007.13108},
  year   = {2020}
}

Comments

Preliminary version

R2 v1 2026-06-23T17:24:37.654Z