Homomorphisms of modules associated with polynomial matrices with infinite elementary divisors

If the inverse of a nonsingular polynomial matrix L has a polynomial part then one can associate with L a module over the ring of proper rational functions, which is related to the structure of L at infinity. In this paper we characterize homomorphisms of such modules.     

A class of marked invariant subspaces with an application to algebraic Riccati equations

Invariant subspaces of a matrix A are considered which are obtained by truncation of a Jordan basis of a generalized eigenspace of A. We characterize those subspaces which are independent of the choice of the Jordan basis. An application to Hamilton matrices and algebraic Riccati equations is given.