Some Characterizations of the Quasi-Projection Pair
摘要
The goal of this article is to study the properties of the quasi-projection pair (P, Q) with projection P and idempotent Q defined on a Hilbert space. We present characterizations of quasi-projection pairs in terms of spectrum, Hilbert space decomposition and norm inequalities. To this end a matrix representation of a quasi-projection pair with respect to their ranges is described.