Abstract
For a Banach algebra and a bounded multiplier T of , there is a new Banach algebra T, related to and T, that has the same underlying space as . We investigate the relationship between the Banach algebras and T. It is shown that is Arens regular (resp. approximately amenable, approximately weakly amenable) if and only if T is, under certain conditions. We show that, for the group algebra L1(G) of a locally compact group G, there exists a multiplier T such that L1(G)T is Arens regular if and only if G is compact, so that, L1(G) and L1(G)T do not have the same properties.