On character amenable Banach algebras

Z. Hu¹ ; M. Sangani Monfared¹ ; T. Traynor¹

¹Department of Mathematics and Statistics University of Windsor Windsor, ON, Canada N9B 3P4

Studia Mathematica, Tome 193 (2009) no. 1, pp. 53-78

Résumé

We obtain characterizations of left character amenable Banach algebras in terms of the existence of left $\phi$-approximate diagonals and left $\phi$-virtual diagonals. We introduce the left character amenability constant and find this constant for some Banach algebras. For all locally compact groups $G$, we show that the Fourier–Stieltjes algebra $B(G)$ is $C$-character amenable with $C2$ if and only if $G$ is compact. We prove that if $A$ is a character amenable, reflexive, commutative Banach algebra, then $A\cong \mathbb C^n$ for some $n\in \mathbb N$. We show that the left character amenability of the double dual of a Banach algebra $A$ implies the left character amenability of $A$, but the converse statement is not true in general. In fact, we give characterizations of character amenability of $L^1(G)^{**}$ and $A(G)^{**}$. We show that a natural uniform algebra on a compact space $X$ is character amenable if and only if $X$ is the Choquet boundary of the algebra. We also introduce and study character contractibility of Banach algebras.

Détail

DOI : 10.4064/sm193-1-3

Keywords: obtain characterizations character amenable banach algebras terms existence phi approximate diagonals phi virtual diagonals introduce character amenability constant constant banach algebras locally compact groups fourier stieltjes algebra c character amenable only compact prove character amenable reflexive commutative banach algebra cong mathbb mathbb character amenability double dual banach algebra implies character amenability converse statement general characterizations character amenability ** ** natural uniform algebra compact space character amenable only choquet boundary algebra introduce study character contractibility banach algebras