Grünbaum's inequality for Gaussian and convex probability measures

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Main Authors: Fradelizi, Matthieu, Langharst, Dylan, Liu, Jiaqian, Sola, Francisco Marín, Tang, Shengyu
Format: Preprint
Published: 2025
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_version_ 1866913944083365888
author Fradelizi, Matthieu
Langharst, Dylan
Liu, Jiaqian
Sola, Francisco Marín
Tang, Shengyu
author_facet Fradelizi, Matthieu
Langharst, Dylan
Liu, Jiaqian
Sola, Francisco Marín
Tang, Shengyu
contents A celebrated result in convex geometry is Grünbaum's inequality, which quantifies how much volume of a convex body can be cut off by a hyperplane passing through its barycenter. In this work, we establish a series of sharp Grünbaum-type inequalities - with equality characterizations - for probability measures under certain concavity assumptions. As an application, we apply the renowned Ehrhard inequality and deduce an ``Ehrhard-Grünbaum'' inequality for the Gaussian measure on $\mathbb{R}^n$, which improves upon the bound derived from its log-concavity. For $s$-concave Radon measures, our framework provides a simpler proof of known results and, more importantly, yields the previously missing equality characterization. This is achieved by gaining new insight into the equality case of their Brunn-Minkowski-type inequality. Moreover, we show that these ``$s$-Grünbaum'' inequalities can hold only when $s > -1$. However, for convex measures on the real line, we prove Grünbaum-type inequalities involving their cumulative distribution function.
format Preprint
id arxiv_https___arxiv_org_abs_2507_06759
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Grünbaum's inequality for Gaussian and convex probability measures
Fradelizi, Matthieu
Langharst, Dylan
Liu, Jiaqian
Sola, Francisco Marín
Tang, Shengyu
Functional Analysis
Metric Geometry
Probability
52A40, 52A38, 46N30
A celebrated result in convex geometry is Grünbaum's inequality, which quantifies how much volume of a convex body can be cut off by a hyperplane passing through its barycenter. In this work, we establish a series of sharp Grünbaum-type inequalities - with equality characterizations - for probability measures under certain concavity assumptions. As an application, we apply the renowned Ehrhard inequality and deduce an ``Ehrhard-Grünbaum'' inequality for the Gaussian measure on $\mathbb{R}^n$, which improves upon the bound derived from its log-concavity. For $s$-concave Radon measures, our framework provides a simpler proof of known results and, more importantly, yields the previously missing equality characterization. This is achieved by gaining new insight into the equality case of their Brunn-Minkowski-type inequality. Moreover, we show that these ``$s$-Grünbaum'' inequalities can hold only when $s > -1$. However, for convex measures on the real line, we prove Grünbaum-type inequalities involving their cumulative distribution function.
title Grünbaum's inequality for Gaussian and convex probability measures
topic Functional Analysis
Metric Geometry
Probability
52A40, 52A38, 46N30
url https://arxiv.org/abs/2507.06759