Arens regularity of ideals in $A(G)$, $A_{cb}(G)$ and $A_M(G)$.

Document Type : Dedicated to Prof. A. T.-M. Lau


Department of Pure Mathematics, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1.


In this paper, we look at the question of when various ideals in the Fourier algebra $A(G)$ or its closures $A_M(G)$ and $A_{cb}(G)$ in, respectively, its multiplier and $cb$-multiplier algebra are Arens regular. We show that in each case, if a non-zero ideal is Arens regular, then the underlying group $G$ must be discrete. In addition, we show that if an ideal $I$ in $A(G)$ has a bounded approximate identity, then it is Arens regular if and only if it is finite-dimensional.


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