Abstract
We are interested in the phenomenon of the essential spectrum instability for a class of unbounded (block) Jacobi matrices. We give a series of sufficient conditions for the matrices from certain classes to have a discrete spectrum on a half-axis of a real line. An extensive list of examples showing the sharpness of obtained results is provided.
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Acknowledgements
Both authors are close friends of Leonid Golinskii, and SK is Leonid’s longtime collaborator. It is our great pleasure to dedicate this article to Leonid’s 65-th anniversary. We wish Leonid many more years of blossoming scientific activity, as well as many nice mathematical results in the distinctive “LG soft power” style. We would like to thank Prof. C. Tretter for helpful remarks on the subject of the paper. SN is partially supported by Grants RSF 15-11-30007, RFBR 16-11-00443a, NCN 2013/BST/04319, K. and A. Wallenberg grant of Wallenberg Association and Royal Swedish Academy of Sciences, and by the project SPbGU N\(^{{\underline{\circ }}}\)11.42.1071.2016. The research presented in the paper was done during his stay at University of Bordeaux in the framework of the “IdEx International Scholars” program. SN would like to acknowledge the financial support of the program, as well as the hospitality of the Institute of Mathematics of Bordeaux where he was hosted.
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Communicated by Sergey Denisov.
To Leonid Golinskii on the occasion of his 65-th anniversary.
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Kupin, S., Naboko, S. On the Instability of the Essential Spectrum for Block Jacobi Matrices. Constr Approx 48, 473–500 (2018). https://doi.org/10.1007/s00365-018-9436-4
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DOI: https://doi.org/10.1007/s00365-018-9436-4
Keywords
- Unbounded (block) Jacobi matrices
- Instability of the essential spectrum
- Levinson’s asymptotic theory
- Gilbert–Pearson subordinacy theory