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We prove sharp inequalities for the average number of affine diameters through the points of a convex body $K$ in ${\mathbb R}^n$. These inequalities hold if $K$ is either a polytope or of dimension two. An example shows that the proof…

Metric Geometry · Mathematics 2014-05-08 Imre Barany , Daniel Hug , Rolf Schneider

We show that the cone-volume measure of a convex body with centroid at the origin satisfies the subspace concentration condition. This implies, among others, a conjectured best possible inequality for the $\mathrm{U}$-functional of a convex…

Metric Geometry · Mathematics 2014-07-29 Károly J. Böröczky , Martin Henk

A packing by a body $K$ is collection of congruent copies of $K$ (in either Euclidean or hyperbolic space) so that no two copies intersect nontrivially in their interiors. A covering by $K$ is a collection of congruent copies of $K$ such…

Metric Geometry · Mathematics 2007-05-23 Lewis Bowen

Let $\mu$ be a probability measure on a separable Banach space $X$. A subset $U\subset X$ is $\mu$-continuous if $\mu(\partial U)=0$. In the paper the $\mu$-continuity and uniform $\mu$-continuity of convex bodies in $X$, especially of…

Functional Analysis · Mathematics 2012-09-03 Anatolij Plichko

In light of the log-Brunn-Minkowski conjecture, various attempts have been made to define the geometric mean of convex bodies. Many of these constructions are fairly complex and/or fail to satisfy some natural properties one would expect of…

Metric Geometry · Mathematics 2024-05-02 René Brandenberg , Florian Grundbacher

To every convex body $K \subseteq \mathbb{R}^d$, one may associate a minimal matrix convex set $\mathcal{W}^{\textrm{min}}(K)$, and a maximal matrix convex set $\mathcal{W}^{\textrm{max}}(K)$, which have $K$ as their ground level. The main…

Operator Algebras · Mathematics 2019-07-04 Benjamin Passer , Orr Shalit , Baruch Solel

The aim of this note is to investigate the properties of the convex hull and the homothetic convex hull functions of a convex body $K$ in Euclidean $n$-space, defined as the volume of the union of $K$ and one of its translates, and the…

Metric Geometry · Mathematics 2021-09-24 Ákos G. Horváth , Zsolt Lángi

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

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

For any origin-symmetric convex body $K$ in $\mathbb{R}^n$ in isotropic position, we obtain the bound: \[ M^*(K) \leq C \sqrt{n} \log(n)^2 L_K ~, \] where $M^*(K)$ denotes (half) the mean-width of $K$, $L_K$ is the isotropic constant of…

Functional Analysis · Mathematics 2014-05-09 Emanuel Milman

In this paper, two main results concerning uniformly continuous retractions are proved. First, an $\alpha$-H\"older retraction from any separable Banach space onto a compact convex subset whose closed linear span is the whole space is…

Functional Analysis · Mathematics 2022-05-26 Rubén Medina

Functions that are piecewise defined are a common sight in mathematics while convexity is a property especially desired in optimization. Suppose now a piecewise-defined function is convex on each of its defining components - when can we…

Classical Analysis and ODEs · Mathematics 2014-08-19 Heinz H. Bauschke , Yves Lucet , Hung M. Phan

In this paper, a new proof of the following result is given: The product of the volumes of an origin symmetric convex bodies $K$ in R^2 and of its polar body is minimal if and only if $K$ is a parallelogram.

Metric Geometry · Mathematics 2010-05-21 Youjiang Lin

The mean width of a convex body is the average distance between parallel supporting hyperplanes when the normal direction is chosen uniformly over the sphere. The Simplex Mean Width Conjecture (SMWC) is a longstanding open problem that says…

Metric Geometry · Mathematics 2023-06-29 Aaron Goldsmith

We prove Gaussian approximation theorems for specific $k$-dimensional marginals of convex bodies which possess certain symmetries. In particular, we treat bodies which possess a 1-unconditional basis, as well as simplices. Our results…

Metric Geometry · Mathematics 2009-01-09 Mark W. Meckes

We study the volume ratio between projections of two convex bodies. Given a high-dimensional convex body $K$ we show that there is another convex body $L$ such that the volume ratio between any two projections of fixed rank of the bodies…

Metric Geometry · Mathematics 2022-11-14 Daniel Galicer , Alexander E. Litvak , Mariano Merzbacher , Damián Pinasco

We present an alternative approach to some results of Koldobsky on measures of sections of symmetric convex bodies, which allows us to extend them to the not necessarily symmetric setting. We prove that if $K$ is a convex body in ${\mathbb…

Metric Geometry · Mathematics 2015-12-31 Giorgos Chasapis , Apostolos Giannopoulos , Dimitris-Marios Liakopoulos

We establish a result which states that regularizing an inverse problem with the gauge of a convex set $C$ yields solutions which are linear combinations of a few extreme points or elements of the extreme rays of $C$. These can be…

Optimization and Control · Mathematics 2018-12-12 Claire Boyer , Antonin Chambolle , Yohann de Castro , Vincent Duval , Frédéric de Gournay , Pierre Weiss

The intersection $L$ of two different non-opposite hemispheres $G$ and $H$ of a $d$-dimensional sphere $S^d$ is called a lune. By the thickness of $L$ we mean the distance of the centers of the $(d-1)$-dimensional hemispheres bounding $L$.…

Metric Geometry · Mathematics 2018-01-08 Marek Lassak , Michał Musielak

It is proved that for a symmetric convex body K in R^n, if for some tau > 0, |K cap (x+tau K)| depends on ||x||_K only, then K is an ellipsoid. As a part of the proof, smoothness properties of convolution bodies ls are studied.

Functional Analysis · Mathematics 2016-09-06 Mathieu Meyer , Shlomo Reisner , M. Schmuckenschlager