The Boolean surface area of polynomial threshold functions

Fuente: arXiv
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Autori principali: Chang, Fan, Slote, Joseph, Volberg, Alexander, Zhang, Haonan
Natura: Preprint
Pubblicazione: 2026
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author Chang, Fan
Slote, Joseph
Volberg, Alexander
Zhang, Haonan
author_facet Chang, Fan
Slote, Joseph
Volberg, Alexander
Zhang, Haonan
contents Polynomial threshold functions (PTFs) are an important low-complexity class of Boolean functions, with strong connections to learning theory and approximation theory. Recent work on learning and testing PTFs has exploited structural and isoperimetric properties of the class, especially bounds on average sensitivity, one of the central themes in the study of PTFs since the Gotsman--Linial conjecture. In this work we study PTFs through the lens of the Boolean surface area (or Talagrand boundary) \[ \mathbf{BSA}[f]=\mathbb{E}|\nabla f|=\mathbb{E}\sqrt{s_{f}(x)}, \] a natural measure of vertex-boundary complexity on the discrete cube. Our main result is that every degree-$d$ PTF has polylogarithmic Boolean surface area: \[ \mathbf{BSA}[f]\le C_d(\log(en))^{C_d}. \] The proof is based on the PTF Restriction Lemma of Kabanets, Kane, and Lu \cite{KKL2017} and proceeds through a tail bound for the pointwise sensitivity. In particular, it controls all subcritical fractional moments of the sensitivity. We also record a random block partition principle for Boolean surface area and an alternative recursive argument following Kane's work \cite{DK} on average sensitivity, which independently yields the weaker bound \[ \mathbf{BSA}[f]\le \exp(C_d\sqrt{\log n}). \]
format Preprint
id arxiv_https___arxiv_org_abs_2604_08095
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The Boolean surface area of polynomial threshold functions
Chang, Fan
Slote, Joseph
Volberg, Alexander
Zhang, Haonan
Computational Complexity
Analysis of PDEs
Classical Analysis and ODEs
Probability
42C10, 30L15, 46B07, 60G46
Polynomial threshold functions (PTFs) are an important low-complexity class of Boolean functions, with strong connections to learning theory and approximation theory. Recent work on learning and testing PTFs has exploited structural and isoperimetric properties of the class, especially bounds on average sensitivity, one of the central themes in the study of PTFs since the Gotsman--Linial conjecture. In this work we study PTFs through the lens of the Boolean surface area (or Talagrand boundary) \[ \mathbf{BSA}[f]=\mathbb{E}|\nabla f|=\mathbb{E}\sqrt{s_{f}(x)}, \] a natural measure of vertex-boundary complexity on the discrete cube. Our main result is that every degree-$d$ PTF has polylogarithmic Boolean surface area: \[ \mathbf{BSA}[f]\le C_d(\log(en))^{C_d}. \] The proof is based on the PTF Restriction Lemma of Kabanets, Kane, and Lu \cite{KKL2017} and proceeds through a tail bound for the pointwise sensitivity. In particular, it controls all subcritical fractional moments of the sensitivity. We also record a random block partition principle for Boolean surface area and an alternative recursive argument following Kane's work \cite{DK} on average sensitivity, which independently yields the weaker bound \[ \mathbf{BSA}[f]\le \exp(C_d\sqrt{\log n}). \]
title The Boolean surface area of polynomial threshold functions
topic Computational Complexity
Analysis of PDEs
Classical Analysis and ODEs
Probability
42C10, 30L15, 46B07, 60G46
url https://arxiv.org/abs/2604.08095