Regularity and amenability of weighted Banach algebras and their second dual on locally compact groups

Abstract

Let $\omega $ be a weight function on a locally compact group G mand let $ M_* (G, \omega ) $ be the subspace of $ M(G , \omega )^* $ consisting of all functionals that vanish at infinity. In this paper, we first investigate the Arens regularity of $ M_* (G, \omega )^* $ and show that $ M_* (G, \omega )^* $ is Arnes regular if and only if G is finite or $ \omega $ is zero cluster. This result is an answer to the question posed and it improves some well-known results. We also give necessary and sufficient criteria for the weight function spaces $ Wap(G , 1/ \omega ) $ and $ Wap(G , 1/ \omega ) $ to be equal to $ C_b (G , 1/ \omega ) $. We prove that for non-compact group G, the Banach algebra $ M_* (G, \omega )^* $ is Arnes regular if and only if $ Wap(G , 1/ \omega ) = C_b (G , 1/ \omega ) $. We then investigate amenability of $ M_* (G, \omega )^* $ and prove that $ M_* (G, \omega )^* $ is amenable and Arnes regular if and only if G is finite.