THERMAL SCIENCE

International Scientific Journal

Authors of this Paper

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Qingmei Bai

,

Alatancang Chen

,

Junjie Huang

POINT SPECTRUM, RESIDUAL SPECTRUM, AND CONTINUOUS SPECTRUM OF UNBOUNDED UPPER TRIANGULAR OPERATOR MATRICES

ABSTRACT
This paper examines the completion of the point spectrum, residual spectrum, and continuous spectrum of an unbounded operator matrix acting in a Hilbert space. The necessary and sufficient conditions for the point spectrum of an unbounded operator matrix to be equal to the union of the point spectra of its diagonal entries are presented.
KEYWORDS
closed operator matrix, point spectrum, residual spectrum, continuous spectrum
PAPER SUBMITTED: 2024-05-07
PAPER REVISED: 2024-07-10
PAPER ACCEPTED: 2024-07-10
PUBLISHED ONLINE: 2025-07-06
DOI REFERENCE: https://doi.org/10.2298/TSCI2503811B
CITATION EXPORT: view in browser or download as text file
THERMAL SCIENCE YEAR 2025, VOLUME 29, ISSUE Issue 3, PAGES [1811 - 1820]
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Point spectrum, residual spectrum, and continuous spectrum of unbounded upper triangular operator matrices

2025 Society of Thermal Engineers of Serbia. Published by the Vinča Institute of Nuclear Sciences, National Institute of the Republic of Serbia, Belgrade, Serbia. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International licence