Half line Titchmarsh-Weyl $m$ functions of vector-valued discrete Schrodinger operators

Abstract: We show that the half-line $m$ functions associated with the vector-valued Schrodinger operators are the elements in the Siegel upper half space. We introduce a metric on the space of $m$ functions associated to the vector-valued discrete Schrodinger operators. Then we show that the action of transfer matrices on these $m$ functions is distance decreasing.