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Journal of Operator Theory

Volume 90, Issue 2, Autumn 2023  pp. 491-522.

On isometric asymptotes of operators quasisimilar to isometries

Authors:  Maria F. Gamal
Author institution:St. Petersburg Branch, V.A. Steklov Institute of Mathematics, Russian Academy of Sciences, Fontanka 27, St. Petersburg, 191023, Russia

Summary:  The notions of isometric and unitary asymptotes was introduced for power bounded operators in 1989 and was generalized in 2016-2019 by Kerchy. In particular, it was shown that there exist operators without unitary asymptote. In this paper operators are constructed which are quasisimilar to isometries and do not have isometric asymptotes. Also a contraction is constructed which is quasisimilar to the unilateral shift of infinite multiplicity and whose isometric asymptote contains a (non-zero) unitary summand.

Keywords: unilateral shift, isometry, unitary operator, quasisimilarity, unitary asymptote

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