Semigroup Forum, ( ISI ), Volume (92), No (1), Year (2016-1) , Pages (304-310)
Title : ( Arens regularity of certain weighted semigroup algebras and countability )
Authors: Hamid Reza Ebrahimi Vishki , Bahram Khodsiani , Ali Rejali ,Access to full-text not allowed by authors
Abstract
In this paper, among other things, we show that for a large class of semi-groups, the Arens regularity of the weighted semigroup algebra ℓ1(S,w) implies the countability of S. This generalizes the main results of Craw and Young [Quart. J. Math.25 (1974), 351-358], stating that every countable semigroup admits a weight w for which ℓ1(S,w) is Arens regular and no uncountable group admits such a weight.