Annihilators in the Bidual of the Generalized Group Algebra of a Discrete Group

Abstract

In this short note, the second dual of generalized group algebra \((\ell ^1(G,\mathcal {A}),*)\) equipped with both Arens product is investigated, where G is any discrete group and \(\mathcal {A}\) is a Banach algebra containing a complemented algebraic copy of \((\ell ^1(\mathbb N),\bullet )\). We give an explicit family of annihilators(w.r.t both the Arens product) in the algebra \(\ell ^1(G,\mathcal {A})^{**}\), arising from non-principal ultrafilters on \({\mathbb {N}}\) and which are not in the toplogical center. As a consequence, we also deduce the fact that \(\ell ^1(G,\mathcal {A})\) is not Strongly Arens irregular.