bipositive isomorphisms on semigroup algebras

Let s be a locally compact foundation semigroup with identity and ma(s) be its semigroup algebra. in the present article, we show that if t is a bipositive isomorphism from ma(s1) onto ma(s2), then t is an isometry and s1 and s2 are isomorphic locally compact semigroups. indeed, we have obtained a generalization of a well-known result of wendel [9] and kawada [6] for locally compact groups to a more general setting of locally compact foundation semigroups. also we show that if t is a bipositive isomorphism from ma(s1) ∗∗ onto ma(s2) ∗∗, then s1 and s2 are isomorphic locally compact semigroups.