Award-winning monograph of the Ferran Sunyer i Balaguer Prize 1997. This book is a self-
contained exposition of the spectral theory of Toeplitz operators with piecewise continuous …

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 …

We give a new proof for the Wedin theorem on the simultaneous unitary similarity
transformation of two orthogonal projections and show that it is equivalent to Halmos' …

We introduce a new concept of unbounded solutions to the operator Riccati equation A1X–
XA0–XVX+ V*= 0 and give a complete description of its solutions V* A1 We also provide a …

We compute the Fredholm index, index (DA), of the operator DA=(d/dt)+ A on L2 (R; H)
associated with the operator path {A (t)} t=−∞∞, where (Af)(t)= A (t) f (t) for ae t∈ R, and …

It is well known that for Banach algebras generated by two idempotents and the identity all
irreducible representations are of order not greater than two. These representations have …

Sum and intersection of linear subspaces in a vector space over a field are fundamental
operations in linear algebra. The purpose of this survey paper is to give a comprehensive …

Factorizations of EP operators Page 1 Linear Algebra and its Applications 429 (2008) 1555–1567
Available online at www.sciencedirect.com www.elsevier.com/locate/laa Factorizations of EP …

The paper is devoted to matrices with flat portions on the boundary of their numerical range.
A constructive criterion for such portions to exist is obtained in case of tridiagonal matrices …

The topic of the present paper is concrete Banach andC*-algebras which are generated by a
finite number of idempotents. Our first result is that, for each finitely generated Banach …