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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">10.17586/2220-8054-2021-12-6-657-663</article-id><article-id custom-type="elpub" pub-id-type="custom">najo-539</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>Monotonicity of the eigenvalues of the two-particle Schrӧdinger operator on a lattice</article-title><trans-title-group xml:lang="ru"><trans-title>Монотонность собственных значений двухчастичного оператора Шредингера на решетке</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Abdullaev</surname><given-names>J. I.</given-names></name><name name-style="western" xml:lang="en"><surname>Abdullaev</surname><given-names>J. I.</given-names></name></name-alternatives><bio xml:lang="en"><p>Mirzo Ulugbek 81, Tashkent 100170;</p><p>University Boulevard 15, Samarkand 140104.</p></bio><email xlink:type="simple">jabdullaev@mail.ru</email><xref ref-type="aff" rid="aff-1"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Khalkhuzhaev</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="en"><p>Mirzo Ulugbek 81, Tashkent 100170;</p><p>University Boulevard 15, Samarkand 140104.</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"><name-alternatives><name name-style="eastern" xml:lang="ru"><surname>Usmonov</surname><given-names>L. S.</given-names></name><name name-style="western" xml:lang="en"><surname>Usmonov</surname><given-names>L. S.</given-names></name></name-alternatives><bio xml:lang="en"><p>University Boulevard 15, Samarkand 140104.</p></bio><email xlink:type="simple">u.lochinbek@bk.ru</email><xref ref-type="aff" rid="aff-2"/></contrib></contrib-group><aff xml:lang="en" id="aff-1"><institution>Institute of Mathematics of the Academy of Sciences of the Republic of Uzbekistan; Samarkand State University</institution><country>Uzbekistan</country></aff><aff xml:lang="en" id="aff-2"><institution>Samarkand State University</institution><country>Uzbekistan</country></aff><pub-date pub-type="collection"><year>2021</year></pub-date><pub-date pub-type="epub"><day>07</day><month>08</month><year>2025</year></pub-date><volume>12</volume><issue>6</issue><fpage>657</fpage><lpage>663</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Abdullaev J.I., Khalkhuzhaev A.M., Usmonov L.S., 2025</copyright-statement><copyright-year>2025</copyright-year><copyright-holder xml:lang="ru">Abdullaev J.I., Khalkhuzhaev A.M., Usmonov L.S.</copyright-holder><copyright-holder xml:lang="en">Abdullaev J.I., Khalkhuzhaev A.M., Usmonov L.S.</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/539">https://nanojournal.ifmo.ru/jour/article/view/539</self-uri><abstract><p>We consider the two-particle Schrodinger operator¨ H(k), (k∈T3 ≡ (−π,π]3 is the total quasimomentum of a system of two particles) corresponding to the Hamiltonian of the two-particle system on the three-dimensional lattice Z3. It is proved that the number N(k) ≡ N(k(1),k(2),k(3)) of eigenvalues below the essential spectrum of the operator H(k) is nondecreasing function in each k(i) ∈ [0,π], i = 1,2,3. Under some additional conditions potential vˆ, the monotonicity of each eigenvalue zn(k) ≡ zn(k(1),k(2),k(3)) of the operator H(k) in k(i) ∈ [0,π] with other coordinates k being fixed is proved.</p></abstract><trans-abstract xml:lang="ru"><p>Рассмотрим двухчастичный оператор Шредингера H(k), (k∈T3≡(—π, π]3 — полный квазиимпульс системы двух частиц), соответствующий гамильтониану двухчастичной системы на трехчастичном размерной решетке Z3 Доказано, что число N(k)≡N(k(1), k(2), k(3)) собственных значений ниже существенного спектра оператора H(k) является неубывающей функцией при каждом k(i)≡[0, π], i = 1, 2, 3. При некоторых дополнительных условиях на потенциал vˆ, доказана монотонность каждого собственного значения zn(k)≡zn(k(1), k(2), k(3)) оператора H(k) в k(i)≡[0, π] при фиксированных остальных координатах k.</p></trans-abstract><kwd-group xml:lang="ru"><kwd>двухчастичный оператор Шрёдингера</kwd><kwd>принцип Бирмана-Швингера</kwd><kwd>полный квазиимпульс</kwd><kwd>монотонность собственных значений</kwd></kwd-group><kwd-group xml:lang="en"><kwd>two-particle Schrӧdinger operator</kwd><kwd>Birman-Schwinger principle</kwd><kwd>total quasimomentum</kwd><kwd>monotonicity of the eigenvalues</kwd></kwd-group></article-meta></front><back><ref-list><title>References</title><ref id="cit1"><label>1</label><citation-alternatives><mixed-citation xml:lang="ru">Bloch I., Dalibard J., and Nascimbene S. Quantum simulations with ultracold quantum gases, Nature Physics, 2012, 8, P. 267–276.</mixed-citation><mixed-citation xml:lang="en">Bloch I., Dalibard J., and Nascimbene S. 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