The convex properties and norm bounds for operator matrices involving contractions

Abstract

In this note, the norm bounds and convex properties of special operator matrices ~H(m)n and ~S(m)n are investigated. When Hilbert space K is infinite dimensional, we firstly show that ~H(m)n = ~H(m)n+1 and ~S(m) n = ~S(m)n+1, for m, n = 1,2,.... Then we get that ~H(m) n is a convex and compact set in the ?* topology. Moreover, some norm bounds for ~H(m) n and ~S(m)n are given.