IUMJ

Title: Amenability properties of Rajchman algebras

Authors: Mahya Ghandehari

Issue: Volume 61 (2012), Issue 3, 1369-1392

Abstract:

Rajchman measures of locally compact abelian groups have been studied for almost a century now, and they play an important role in the study of trigonometric series. Eymard's influential work allowed generalizing these measures to the case of \emph{non-abelian} locally compact groups $G$. The Rajchman algebra of $G$, which we denote by $B_0(G)$, is the set of all elements of the Fourier--Stieltjes algebra that vanish at infinity. In the present article, we characterize the locally compact groups that have amenable Rajchman algebras. We show that $B_0(G)$ is amenable if and only if $G$ is compact and almost abelian. On the other extreme, we present many examples of locally compact groups, such as non-compact abelian groups and infinite solvable groups, for which $B_0(G)$ fails to even have an approximate identity.