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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 pub-id-type="doi">10.17586/2220-8054-2023-14-5-518-529</article-id><article-id custom-type="elpub" pub-id-type="custom">najo-288</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 discrete spectrum of the Schrödinger operator using the 2+1 fermionic trimer on the lattice</article-title><trans-title-group xml:lang="ru"><trans-title>О дискретном спектре оператора шредингера, соответствующего 2+1 фермионному тримеру на решетке</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author" corresp="yes"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0003-0569-6780</contrib-id><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Халхужаев</surname><given-names>A. M.</given-names></name><name name-style="western" xml:lang="en"><surname>Khalkhuzhaev</surname><given-names>A. M.</given-names></name></name-alternatives><bio xml:lang="ru"><p> Халхужаев Ахмад Мияссарович - аспирант Самаркандского государственного университета</p><p>г. Самарканд,  Университетский бульвар 15</p></bio><bio xml:lang="en"><p>Ahmad M. Khalkhuzhaev</p><p>Mirzo Ulugbek 81, 100170</p></bio><email xlink:type="simple">ahmad_x@mail.ru</email><xref ref-type="aff" rid="aff-1"/></contrib><contrib contrib-type="author" corresp="yes"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0001-5439-8729</contrib-id><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Хужамиеров</surname><given-names>И. А.</given-names></name><name name-style="western" xml:lang="en"><surname>Khujamiyorov</surname><given-names>I. A.</given-names></name></name-alternatives><bio xml:lang="en"><p>Islom A. Khujamiyorov</p><p>University Boulevard 15, Samarkand 140104</p></bio><email xlink:type="simple">xujamiyorov1990@mail.ru</email><xref ref-type="aff" rid="aff-2"/></contrib></contrib-group><aff-alternatives id="aff-1"><aff xml:lang="ru"><institution>Институт Математики имени В.И.Романовского Академии наук Республики Узбекистан,  начальник Самаркандского отделения</institution></aff><aff xml:lang="en"><institution>V. I. Romanovsky Institute of Mathematics of the Academy of Sciences of the Republic of Uzbekistan</institution></aff></aff-alternatives><aff xml:lang="en" id="aff-2"><institution>Samarkand State University</institution><country>Uzbekistan</country></aff><pub-date pub-type="collection"><year>2023</year></pub-date><pub-date pub-type="epub"><day>08</day><month>06</month><year>2025</year></pub-date><volume>14</volume><issue>5</issue><fpage>518</fpage><lpage>529</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Khalkhuzhaev A.M., Khujamiyorov I.A., 2025</copyright-statement><copyright-year>2025</copyright-year><copyright-holder xml:lang="ru">Халхужаев A.M., Хужамиеров И.А.</copyright-holder><copyright-holder xml:lang="en">Khalkhuzhaev A.M., Khujamiyorov I.A.</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/288">https://nanojournal.ifmo.ru/jour/article/view/288</self-uri><abstract><p>We consider the three-particle discrete Schrödinger operator H; (K); K 2 T3, associated with the three-particle Hamiltonian (two of them are fermions with mass 1 and one of them is arbitrary with mass m = 1=  &lt; 1), interacting via pair of repulsive contact potentials &gt; 0 on a three-dimensional lattice Z3. It is proved that there are critical values of mass ratios  = 1 and  = 2 such that if  2 (0; 1), then the operator H; (0) has no eigenvalues. If  2 ( 1; 2), then the operator H; (0) has a unique eigenvalue; if  &gt; 2, then the operator H; (0) has three eigenvalues lying to the right of the essential spectrum for all sufficiently large values of the interaction energy.</p></abstract><trans-abstract xml:lang="ru"><p>Рассматривается трехчастичный дискретный оператор Шредингера 〖 H〗_(μ,γ)(K), K∈T^3, ассоциированный с гамильтонианом системы трех частиц (две - фермионы с массой 1 и одна - произвольная с массой m=1/γ&lt;1), взаимодействующих с помощью парных отталкивающих контактных потенциалов μ&gt;0 на трехмерной решетке Z^3. Доказано, что существуют критические значения отношений масс γ= γ_1 и γ= γ_2такие, что если  γ∈(0, γ_1), то оператор 〖 H〗_(μ,γ)(0) не имеет собственных значений, если γϵ( γ_1, γ_2), то имеет единственное собственное значение, если  γ&gt;γ_2 то имеет три собственных значения, лежащих правее существенного спектра при всех достаточно больших значениях энергии взаимодействия μ.</p></trans-abstract><kwd-group xml:lang="ru"><kwd>Оператор Шредингера</kwd><kwd>гамильтониан</kwd><kwd>контактный потенциал</kwd><kwd>фермион</kwd><kwd>собственное значение</kwd><kwd>квазиимпульс</kwd><kwd>инвариантное подпространство</kwd><kwd>оператор Фаддеева</kwd></kwd-group><kwd-group xml:lang="en"><kwd>Schrödinger operator</kwd><kwd>Hamiltonian</kwd><kwd>contact potential</kwd><kwd>fermion</kwd><kwd>eigenvalue</kwd><kwd>quasi-momentum</kwd><kwd>invariant subspace</kwd><kwd>Faddeev operator</kwd></kwd-group><funding-group><funding-statement xml:lang="en">We thank unknown referee for careful reading of the manuscript and useful comments.</funding-statement></funding-group></article-meta></front><back><ref-list><title>References</title><ref id="cit1"><label>1</label><citation-alternatives><mixed-citation xml:lang="ru">Michelangeli A., Ottolini A. 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