Cross-connections and variants of the full transformation semigroup

Abstract

Cross-connection theory propounded by K. S. S. Nambooripad describes the ideal structure of a regular semigroup using the categories of principal left (right) ideals. A variant $\mathscr{T}_X^θ$ of the full transformation semigroup $(\mathscr{T}_X,\cdot)$ for an arbitrary $θ\in \mathscr{T}_X$ is the semigroup $\mathscr{T}_X^θ= (\mathscr{T}_X,\ast)$ with the binary operation $α\ast β= α\cdotθ\cdotβ$ where $α, β\in \mathscr{T}_X$. In this article, we describe the ideal structure of the regular part $Reg(\mathscr{T}_X^θ)$ of the variant of the full transformation semigroup using cross-connections. We characterize the constituent categories of $Reg(\mathscr{T}_X^θ)$ and describe how they are \emph{cross-connected} by a functor induced by the sandwich transformation $θ$. This lead us to a structure theorem for the semigroup and give the representation of $Reg(\mathscr{T}_X^θ)$ as a cross-connection semigroup. Using this, we give a description of the biordered set and the sandwich sets of the semigroup.