Topological convolution algebras

Abstract

In this paper we introduce a dual of reflexive Fréchet counterpart of Banach algebras of the form ⋃p∈NΦp′ (where the Φp′ are (dual of) Banach spaces with associated norms ‖⋅‖p), which carry inequalities of the form ‖ab‖p⩽Ap,q‖a‖q‖b‖p and ‖ba‖p⩽Ap,q‖a‖q‖b‖p for p>q+d, where d is preassigned and Ap,q is a constant. We study the functional calculus and the spectrum of the elements of these algebras. We then focus on the particular case Φp′=L2(S,μp), where S is a Borel semi-group in a locally compact group G, and multiplication is convolution. We give a sufficient condition on the measures μp for such inequalities to hold. Finally we present three examples, one is the algebra of germs of holomorphic functions in zero, the second related to Dirichlet series and the third in the setting of non-commutative stochastic distributions.