Generalized module extension Banach algebras: Derivations and weak amenability

Abstract

Let A and X be Banach algebras and let X be an algebraic Banach A-module. Then the ℓ^-1direct sum A x X equipped with the multiplication (a; x)(b; y) = (ab; ay + xb + xy) (a; b ∈ A; x; y ∈ X) is a Banach algebra, denoted by A ⋈ X, which will be called "a generalized module extension Banach algebra". Module extension algebras, Lau product and also the direct sum of Banach algebras are the main examples satisfying this framework. We characterize the structure of n-dual valued (n ∈ N) derivations on A ⋈ X from which we investigate the n-weak amenability for the algebra A ⋈ X: We apply the results and the techniques of proofs for presenting some older results with simple direct proofs.

Mathematics Subject Classication (2010): 46H20, 46H25.

Key words: Banach algebra, derivation, n-weak amenability.