A gentle guide to the basics of two projections theory
The authors nicely survey the foundamental theory of two projections including Halmos' two projections theorem [see \textit{P.\,R.\thinspace Halmos}, Trans.\ Am.\ Math.\ Soc.\ 144, 381--389 (1969; Zbl 0187.05503)] and Roch, Silbermann, Gohberg, and Krupnik's theorem on two idempotents in Banach algebras [see \textit{I.\,Gohberg} and \textit{N.\,Krupnik}, Integral Equations Oper.\ Theory 15, No.\,6, 991--1010 (1992; Zbl 0795.46043), Integral Equations Oper.\ Theory 16, No.\,4, 514--529 (1993; Zbl 0811.46044) as well as \textit{S.\,Roch} and \textit{B.\,Silbermann}, Integral Equations Oper.\ Theory 11, No.\,3, 385--419 (1988; Zbl 0658.47050)].
scientific article; zbMATH DE number 5667879
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