Abstract:
We consider the normal extensions of semigroups. The reduced semigroup $C^*$-algebras are associated
with these extensions. We study the structure of a Banach module on the underlying space of the
reduced semigroup $C^*$-algebra defined for a semigroup that is an extension of another semigroup by a
finite group
Keywords:cancellative semigroup, normal extension of semigroup, reduced semigroup $C^*$-algebra, Banach module, free Banach module.