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Gr\"unbaum's inequality gives sharp bounds between the volume of a convex body and its part cut off by a hyperplane through the centroid of the body. We provide a generalization of this inequality for hyperplanes that do not necessarily…

Metric Geometry · Mathematics 2024-10-11 Brayden Letwin , Vladyslav Yaskin

Let $1\leq i \leq k < n$ be integers. We prove the following exact inequalities for any convex body $K\subset\mathbb{R}^n$ with centroid at the origin, and any $k$-dimensional subspace $E\subset \mathbb{R}^n$: \begin{align*} &V_i \big(…

Metric Geometry · Mathematics 2018-09-18 Matthew Stephen , Vladyslav Yaskin

Given a hyperplane $H$ cutting a compact, convex body $K$ of positive Lebesgue measure through its centroid, Gr\"unbaum proved that $$\frac{|K\cap H^+|}{|K|}\geq \left(\frac{n}{n+1}\right)^n,$$ where $H^+$ is a half-space of boundary $H$.…

Metric Geometry · Mathematics 2025-07-16 Luca Tanganelli Castrillón

We show \begin{align*} \frac{ \int_{E \cap \theta^+} f(x) dx }{ \int_E f(x) dx } \geq \left(\frac{k \gamma+1}{(n+1) \gamma+1}\right)^{\frac{k \gamma+1}{\gamma}} \end{align*} for all $k$-dimensional subspaces $E\subset\mathbb{R}^n$,…

Metric Geometry · Mathematics 2017-11-06 Sergii Myroshnychenko , Matthew Stephen , Ning Zhang

A celebrated result in convex geometry is Gr\"unbaum'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 Gr\"unbaum-type…

Functional Analysis · Mathematics 2025-07-17 Matthieu Fradelizi , Dylan Langharst , Jiaqian Liu , Francisco Marín Sola , Shengyu Tang

We generalize Gr\"unbaum's classical inequality in convex geometry to curved spaces with nonnegative Ricci curvature, precisely, to $\mathrm{RCD}(0,N)$-spaces with $N \in (1,\infty)$ as well as weighted Riemannian manifolds of…

Metric Geometry · Mathematics 2025-10-24 Victor-Emmanuel Brunel , Shin-ichi Ohta , Jordan Serres

We construct a convex body $K$ in $\mathbb{R}^n$, $n \geq 5$, with the property that there is exactly one hyperplane $H$ passing through $c(K)$, the centroid of $K$, such that the centroid of $K\cap H$ coincides with $c(K)$. This provides…

Metric Geometry · Mathematics 2024-11-11 S. Myroshnychenko , K. Tatarko , V. Yaskin

The average section functional ${\rm as}(K)$ of a centered convex body in ${\mathbb R}^n$ is the average volume of central hyperplane sections of $K$: \begin{equation*}{\rm as}(K)=\int_{S^{n-1}}|K\cap \xi^{\perp }|\,d\sigma (\xi…

Metric Geometry · Mathematics 2016-07-19 Silouanos Brazitikos , Susanna Dann , Apostolos Giannopoulos , Alexander Koldobsky

In this paper, we obtain the best possible value of the absolute constant $C$ such that for every isotropic convex body $K \subseteq \mathbb{R}^n$ the following inequality (which was proved by Klartag and reduces the hyperplane conjecture…

Metric Geometry · Mathematics 2022-10-18 Javier Martín-Goñi

We provide general inequalities that compare the surface area S(K) of a convex body K in ${\mathbb R}^n$ to the minimal, average or maximal surface area of its hyperplane or lower dimensional projections. We discuss the same questions for…

Metric Geometry · Mathematics 2019-08-15 Apostolos Giannopoulos , Alexander Koldobsky , Petros Valettas

The inequality of Berwald is a reverse-H\"older like inequality for the $p$th average, $p\in (-1,\infty),$ of a non-negative, concave function over a convex body in $\mathbb{R}^n.$ We prove Berwald's inequality for averages of functions…

Metric Geometry · Mathematics 2025-06-04 Dylan Langharst , Eli Putterman

We prove a generalization of the hyperplane inequality for intersection bodies, where volume is replaced by an arbitrary measure $\mu$ with even continuous density and sections are of arbitrary dimension $n-k,\ 1\le k <n.$ If $K$ is a…

Metric Geometry · Mathematics 2011-08-15 Alexander Koldobsky , Dan Ma

If $K\subset\mathbb{R}^n$ is a convex body and $\Gamma_pK$ is the $p$-centroid body of $K$, the $L_p$ Busemann-Petty centroid inequality states that $\vol(\Gamma_pK) \geq \vol(K)$, with equality if and only if $K$ is an ellipsoid centered…

Functional Analysis · Mathematics 2025-03-14 Julian Haddad , Carlos Hugo Jimenez , Leticia Alves da Silva

The Wills functional $\mathcal{W}(K)$ of a convex body $K$, defined as the sum of its intrinsic volumes $\mathrm{V}_i(K)$, turns out to have many interesting applications and properties. In this paper we make profit of the fact that it can…

Metric Geometry · Mathematics 2020-02-17 David Alonso-Gutiérrez , María A. Hernández Cifre , Jesús Yepes Nicolás

We generalize the classical Hardy and Faber-Krahn inequalities to arbitrary functions on a convex body $\Omega \subset \mathbb{R}^n$, not necessarily vanishing on the boundary $\partial \Omega$. This reduces the study of the Neumann…

Spectral Theory · Mathematics 2015-08-14 Alexander V. Kolesnikov , Emanuel Milman

We give an alternative proof of a recent result of Klartag on the existence of almost subgaussian linear functionals on convex bodies. If $K$ is a convex body in ${\mathbb R}^n$ with volume one and center of mass at the origin, there exists…

Functional Analysis · Mathematics 2007-05-23 Apostolos Giannopoulos , Alain Pajor , Grigoris Paouris

The famous Minkowski inequality provides a sharp lower bound for the mixed volume $V(K,M[n-1])$ of two convex bodies $K,M\subset\mathbb{R}^n$ in terms of powers of the volumes of the individual bodies $K$ and $M$. The special case where $K$…

Metric Geometry · Mathematics 2020-12-04 Daniel Hug , Károly Böröczky

We state a general formula to compute the volume of the intersection of the regular $n$-simplex with some $k$-dimensional subspace. It is known that for central hyperplanes the one through the centroid containing $n-1$ vertices gives the…

Metric Geometry · Mathematics 2019-11-21 Hauke Dirksen

Gr\"unbaum's inequality guarantees that the centroid of a convex body has halfspace depth at least $1/e$: every halfspace containing the centroid captures at least a $1/e$ fraction of the body's volume. For mixed-integer convex sets…

Optimization and Control · Mathematics 2026-03-03 Hongyu Cheng , Amitabh Basu

The covariogram g_K(x) of a convex body K \subseteq E^d is the function which associates to each x \in E^d the volume of the intersection of K with K+x. Matheron asked whether g_K determines K, up to translations and reflections in a point.…

Metric Geometry · Mathematics 2007-05-23 Gennadiy Averkov , Gabriele Bianchi
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