Semigroups of linear transformations whose restrictions belong to a general linear group

Let $V$ be a vector space and $U$ a fixed subspace of $V$. We denote the semigroup of all linear transformations on $V$ under composition of functions by $L(V)$. In this paper, we study the semigroup of all linear transformations on $V$ whose restrictions belong to the general linear group $GL(U)$, denoted by $L_{GL(U)}(V)$. More precisely, we consider the subsemigroup $$L_{GL(U)}(V)=\{\alpha\in L(V):\alpha|_U\in GL(U)\}$$ of $L(V)$. In this work, Green's relations and ideals of this semigroup are described. Then we also determine the minimal ideal and the set of all minimal idempotents of it. Moreover, we establish an isomorphism theorem when $V$ is a finite dimensional vector space over a finite field. Finally, we find its generating set.