On operator Connes-amenability of the Fourier-Stieltjes algebra

TL;DR

This paper investigates the conditions under which the Fourier-Stieltjes algebra B(G) of a group G is operator Connes-amenable, providing new examples of groups where this property does not hold.

Contribution

It identifies the first known examples of groups G for which B(G) is not operator Connes-amenable, advancing understanding of this property in harmonic analysis.

Findings

B(G) is not operator Connes-amenable for non-compact groups with property (T) and finite almost periodic compactification.

B(G) is not operator Connes-amenable for discrete groups lacking the factorization property.

The paper clarifies the relationship between group properties and operator Connes-amenability of B(G).

Abstract

Runde and Spronk showed in 2004 that there are non-amenable groups $G$, including $\mathbb F_2$, {whose Fourier-Stieltjes algebra, $B(G)$,} is operator Connes-amenable. This result was surprising since the measure algebra $M(G)$ is Connes-amenable if and only if $G$ is amenable, which might lead one to guess that $B(G)$ should be operator Connes-amenable if and only if $G$ is amenable. This leads to the question: for which groups $G$ is $B(G)$ operator Connes-amenable? We make progress on this problem by {exhibiting} the first examples of groups {for which $B(G)$ is not operator Connes-amenable}. More specifically, we show that $B(G)$ is not operator Connes-amenable when $G$ is a non-compact locally compact group with property (T) and finite almost periodic compactification, or when $G$ is a discrete group without the factorization property.