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Benoît Kloeckner

Publications and source records attributed to Benoît Kloeckner.

23 records · Page 2Linked to original sources
arXiv2013

Coloring distance graphs: a few answers and many questions

Given a metric space and a set of distances, one constructs the associated distance graph by taking as vertices the points of the space and as edges the pairs whose distance is in the given set. It is a longstanding open question to determine the chromatic number of the graph obtained from the Euclidean plane and a set reduced to one distance. Surprisingly, while many variants of this problem have been studied, only a few non-Euclidean spaces seem to have been seriously considered. In this paper, we consider the planar translation-invariant metrics and the hyperbolic plane. We answer questions of Johnson and Szlam, prove a few other results, and ask many questions.

math.CO↗
arXiv2013

Polarités définies par un triangle

A polarity of a projective plane is a map, often assumed to be involutive, mapping a generic point to a generic line and reciprocally. The most classical polarity is the polarity with respect to a conic, but other exist: the harmonic polarity with respect to a triangle, the polarities with respect to high-degree algebraic curve, the polarities with respect to a convex set. In this article, we introduce a polarity with respect to a triangle motivated by a question on duality of projective frames. We show that the four polarities above apply to a triangle and in fact coincide. This result is an opportunity to review nice concepts of projective geometry, linear algebra and convex geometry.

math.DG↗
arXiv2013

A geometric study of Wasserstein spaces: Hadamard spaces

Optimal transport enables one to construct a metric on the set of (sufficiently small at infinity) probability measures on any (not too wild) metric space X, called its Wasserstein space W(X). In this paper we investigate the geometry of W(X) when X is a Hadamard space, by which we mean that $X$ has globally non-positive sectional curvature and is locally compact. Although it is known that -except in the case of the line- W(X) is not non-positively curved, our results show that W(X) have large-scale properties reminiscent of that of X. In particular we define a geodesic boundary for W(X) that enables us to prove a non-embeddablity result: if X has the visibility property, then the Euclidean plane does not admit any isometric embedding in W(X).

math.MG↗
arXiv2007

Global rigidity in CR geometry: the Schoen-Webster theorem

Schoen-Webster theorem asserts a pseudoconvex CR manifold whose automorphism group acts non properly is either the standard sphere or the Heisenberg space. The purpose of this paper is to survey successive works around this result and then provide a short geometric proof in the compact case.

math.DG↗