Haar Null Closed and Convex Sets in Separable Banach Spaces

Abstract

Haar null sets were introduced by J.P.R. Christensen in 1972 to extend the notion of sets with zero Haar measure to nonlocally compact Polish groups. In 2013, U.B. Darij defined a categorical version of Haar null sets, which he named Haar meagre sets. The present paper aims to show that, whenever $C$ is a closed, convex subset of a separable Banach space, $C$ is Haar null if and only if $C$ is Haar meagre. We then use this fact to improve a theorem of E. Matoušková and to solve a conjecture proposed by Esterle, Matheron and Moreau. Finally, we apply the main theorem to find a characterisation of separable Banach lattices whose positive cone is not Haar null.

11 pages. v2: Section 4 has been extensively rewritten and improved. Corollary 3.6 has a new proof. Fixed typos. v3: Accepted version for publication

References in corpus (1)

• Compactivorous Sets in Banach Spaces

Cited by in corpus (1)

• A Topological Characterisation of Haar Null Convex Sets