Document Type
Article
Department/Program
Mathematics
Journal Title
Linear Algebra and Its Applications
Pub Date
2010
Volume
432
Issue
6
First Page
1412
Abstract
This paper is a survey of the basics of the theory of two projections. It contains in particular the theorem by Halmos on two orthogonal projections and Roch, Silbermann, Gohberg, and Krupnik's theorem on two idempotents in Banach algebras. These two theorems, which deliver the desired results usually very quickly and comfortably, are missing or wrongly cited in many recent publications on the topic, The paper is intended as a gentle guide to the field. The basic theorems are precisely stated, some of them are accompanied by full proofs, others not, but precise references are given in each case, and many examples illustrate how to work with the theorems. (C) 2009 Elsevier Inc. All rights reserved.
Recommended Citation
Boettcher, A. and Spitkovsky, I. M., A gentle guide to the basics of two projections theory (2010). Linear Algebra and Its Applications, 432(6), 1412-1459.
10.1016/j.laa.2009.11.002
DOI
10.1016/j.laa.2009.11.002
