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<article article-type="research-article" dtd-version="1.3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xml:lang="en"><front><journal-meta><journal-id journal-id-type="publisher-id">najo</journal-id><journal-title-group><journal-title xml:lang="en">Nanosystems: Physics, Chemistry, Mathematics</journal-title><trans-title-group xml:lang="ru"><trans-title>Наносистемы: физика, химия, математика</trans-title></trans-title-group></journal-title-group><issn pub-type="ppub">2220-8054</issn><issn pub-type="epub">2305-7971</issn><publisher><publisher-name>Университет ИТМО</publisher-name></publisher></journal-meta><article-meta><article-id custom-type="elpub" pub-id-type="custom">najo-1026</article-id><article-categories><subj-group subj-group-type="heading"><subject>Research Article</subject></subj-group><subj-group subj-group-type="section-heading" xml:lang="en"><subject>MATHEMATICS</subject></subj-group><subj-group subj-group-type="section-heading" xml:lang="ru"><subject>МАТЕМАТИКА</subject></subj-group></article-categories><title-group><article-title>On the number of eigenvalues of the family of operator matrices</article-title><trans-title-group xml:lang="ru"><trans-title></trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="western" xml:lang="en"><surname>Muminov</surname><given-names>M. I.</given-names></name></name-alternatives><bio xml:lang="en"><p>81310 UTM Johor Bahru</p></bio><email xlink:type="simple">mmuminov@mail.ru</email><xref ref-type="aff" rid="aff-1"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="western" xml:lang="en"><surname>Rasulov</surname><given-names>T. H.</given-names></name></name-alternatives><bio xml:lang="en"><p>11 M. Ikbol str., Bukhara, 200100</p></bio><email xlink:type="simple">rth@mail.ru</email><xref ref-type="aff" rid="aff-2"/></contrib></contrib-group><aff xml:lang="en" id="aff-1"><institution>Universiti Teknologi Malaysia, Faculty of Science, Department of Mathematical Sciences</institution><country>Malaysia</country></aff><aff xml:lang="en" id="aff-2"><institution>Bukhara State University, Faculty of Physics and Mathematics</institution><country>Uzbekistan</country></aff><pub-date pub-type="collection"><year>2014</year></pub-date><pub-date pub-type="epub"><day>18</day><month>08</month><year>2025</year></pub-date><volume>5</volume><issue>5</issue><fpage>619</fpage><lpage>625</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Muminov M.I., Rasulov T.H., 2025</copyright-statement><copyright-year>2025</copyright-year><copyright-holder xml:lang="ru">Muminov M.I., Rasulov T.H.</copyright-holder><copyright-holder xml:lang="en">Muminov M.I., Rasulov T.H.</copyright-holder><license xml:lang="ru" license-type="creative-commons-attribution" xlink:href="https://creativecommons.org/licenses/by/4.0/" xlink:type="simple"><license-p>Данная работа распространяется под лицензией Creative Commons Attribution 4.0.</license-p></license><license xml:lang="en" license-type="creative-commons-attribution" xlink:href="https://creativecommons.org/licenses/by/4.0/" xlink:type="simple"><license-p>This work is licensed under a Creative Commons Attribution 4.0 License.</license-p></license></permissions><self-uri xlink:href="https://nanojournal.ifmo.ru/jour/article/view/1026">https://nanojournal.ifmo.ru/jour/article/view/1026</self-uri><abstract><p>We consider the family of operator matrices H(K), K ∈ T3 := (−π; π]3 acting in the direct sum of zero-, one- and two-particle subspaces of the bosonic Fock space. We find a finite set Λ ⊂ T3 to establish the existence of infinitely many eigenvalues of H(K) for all K ∈ Λ when the associated Friedrichs model has a zero energy resonance. It is found that for every K ∈ Λ, the number N (K, z) of eigenvalues of H(K) lying on the left of z, z &lt; 0, satisfies the asymptotic relation lim z→−0 N (K, z)| log |z||−1 = U0 with 0 &lt; U0 &lt; ∞, independently on the cardinality of Λ. Moreover, we show that for any K ∈ Λ the operator H(K) has a finite number of negative eigenvalues if the associated Friedrichs model has a zero eigenvalue or a zero is the regular type point for positive definite Friedrichs model.</p></abstract><kwd-group xml:lang="en"><kwd>operator matrix</kwd><kwd>bosonic Fock space</kwd><kwd>annihilation and creation operators</kwd><kwd>Friedrichs model</kwd><kwd>essential spectrum</kwd><kwd>asymptotics</kwd></kwd-group><funding-group><funding-statement xml:lang="en">This work was supported by the IMU Einstein Foundation Program. T. H. 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