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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-1265</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>Note on 2D Schrödinger operators with δ-interactions on angles and crossing lines</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>Lotoreichik</surname><given-names>V.</given-names></name></name-alternatives><bio xml:lang="en"><p>Steyrergasse 30, 8010 Graz</p></bio><email xlink:type="simple">lotoreichik@math.tugraz.at</email><xref ref-type="aff" rid="aff-1"/></contrib></contrib-group><aff xml:lang="en" id="aff-1"><institution>Technische Universität Graz, Institut für Numerische Mathematik</institution><country>Austria</country></aff><pub-date pub-type="collection"><year>2013</year></pub-date><pub-date pub-type="epub"><day>22</day><month>08</month><year>2025</year></pub-date><volume>4</volume><issue>2</issue><fpage>166</fpage><lpage>172</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Lotoreichik V., 2025</copyright-statement><copyright-year>2025</copyright-year><copyright-holder xml:lang="ru">Lotoreichik V.</copyright-holder><copyright-holder xml:lang="en">Lotoreichik V.</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/1265">https://nanojournal.ifmo.ru/jour/article/view/1265</self-uri><abstract><p>In this note we sharpen the lower bound previously obtained by Lobanov et al [LLP10] for the spectrum of the 2D Schrödinger operator with a δ-interaction supported on a planar angle. Using the same method we obtain the lower bound on the spectrum of the 2D Schrödinger operator with a δ-interaction supported on crossing straight lines. The latter operators arise in the three-body quantum problem with δ-interactions between particles.</p></abstract><kwd-group xml:lang="en"><kwd>Schrödinger operators</kwd><kwd>δ-interactions</kwd><kwd>spectral estimates</kwd></kwd-group><funding-group><funding-statement xml:lang="en">The work was supported by Austrian Science Fund (FWF): project P 25162-N26 and partially supported by the Ministry of Education and Science of Russian Federation: project 14.B37.21.0457.</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">[BLL13] J. Behrndt, M. Langer, and V. Lotoreichik, Schr¨odinger operators with δ and δ′-potentials supported on hypersurfaces, Ann. Henri Poincar ´e, 14, P. 385–423 (2013).</mixed-citation><mixed-citation xml:lang="en">[BLL13] J. Behrndt, M. Langer, and V. Lotoreichik, Schr¨odinger operators with δ and δ′-potentials supported on hypersurfaces, Ann. Henri Poincar ´e, 14, P. 385–423 (2013).</mixed-citation></citation-alternatives></ref><ref id="cit2"><label>2</label><citation-alternatives><mixed-citation xml:lang="ru">[BEKS94] J.F. Brasche, P. Exner, Yu.A. Kuperin, and P. ˇ Seba, Schr¨odinger operators with singular inter actions, J. Math. Anal. Appl., 184, P. 112–139 (1994).</mixed-citation><mixed-citation xml:lang="en">[BEKS94] J.F. Brasche, P. Exner, Yu.A. Kuperin, and P. ˇ Seba, Schr¨odinger operators with singular inter actions, J. Math. Anal. Appl., 184, P. 112–139 (1994).</mixed-citation></citation-alternatives></ref><ref id="cit3"><label>3</label><citation-alternatives><mixed-citation xml:lang="ru">[BEW08] B.M. Brown, M. S. P. Eastham, and I. Wood, An example on the discrete spectrum of a star graph, in Analysis on Graphs and Its Applications, Proceedings of Symposia in Pure Mathematics, American Mathematical Society (2008).</mixed-citation><mixed-citation xml:lang="en">[BEW08] B.M. Brown, M. S. P. Eastham, and I. Wood, An example on the discrete spectrum of a star graph, in Analysis on Graphs and Its Applications, Proceedings of Symposia in Pure Mathematics, American Mathematical Society (2008).</mixed-citation></citation-alternatives></ref><ref id="cit4"><label>4</label><citation-alternatives><mixed-citation xml:lang="ru">[BEW09] B.M. Brown, M. S. P. Eastham, and I. Wood, Estimates for the lowest eigenvalue of a star graph, J. Math. Anal. Appl., 354, P. 24–30 (2009).</mixed-citation><mixed-citation xml:lang="en">[BEW09] B.M. Brown, M. S. P. Eastham, and I. Wood, Estimates for the lowest eigenvalue of a star graph, J. Math. Anal. Appl., 354, P. 24–30 (2009).</mixed-citation></citation-alternatives></ref><ref id="cit5"><label>5</label><citation-alternatives><mixed-citation xml:lang="ru">[CDR06] H. Cornean, P. Duclos, and B. Ricaud, On critical stability of three quantum charges interacting through delta potentials, Few-Body Systems, 38, P. 125–131 (2006).</mixed-citation><mixed-citation xml:lang="en">[CDR06] H. Cornean, P. Duclos, and B. Ricaud, On critical stability of three quantum charges interacting through delta potentials, Few-Body Systems, 38, P. 125–131 (2006).</mixed-citation></citation-alternatives></ref><ref id="cit6"><label>6</label><citation-alternatives><mixed-citation xml:lang="ru">[CDR08] H. Cornean, P. Duclos, and B. Ricaud, On the skeleton method and an application to a quantum scissor, in Analysis on graphs and its applications, Proc. Sympos. Pure Math. Amer. Math. Soc. Providence (2008).</mixed-citation><mixed-citation xml:lang="en">[CDR08] H. Cornean, P. Duclos, and B. Ricaud, On the skeleton method and an application to a quantum scissor, in Analysis on graphs and its applications, Proc. Sympos. Pure Math. Amer. Math. Soc. Providence (2008).</mixed-citation></citation-alternatives></ref><ref id="cit7"><label>7</label><citation-alternatives><mixed-citation xml:lang="ru">[E08] P. Exner, Leaky quantum graphs: a review, in Analysis on graphs and its applications, Proc. Sympos. Pure Math. Amer. Math. Soc. Providence (2008).</mixed-citation><mixed-citation xml:lang="en">[E08] P. Exner, Leaky quantum graphs: a review, in Analysis on graphs and its applications, Proc. Sympos. Pure Math. Amer. Math. Soc. Providence (2008).</mixed-citation></citation-alternatives></ref><ref id="cit8"><label>8</label><citation-alternatives><mixed-citation xml:lang="ru">[EI01] P. Exner and I. Ichinose, Geometrically induced spectrum in curved leaky wires, J. Phys. A, 34, P. 1439–1450 (2001).</mixed-citation><mixed-citation xml:lang="en">[EI01] P. Exner and I. Ichinose, Geometrically induced spectrum in curved leaky wires, J. Phys. A, 34, P. 1439–1450 (2001).</mixed-citation></citation-alternatives></ref><ref id="cit9"><label>9</label><citation-alternatives><mixed-citation xml:lang="ru">[EN03] P. Exner and K. Nˇemcov´a, Leaky quantum graphs: approximations by point-interaction Hamiltoni ans, J. Phys. A, 36, P. 10173–10193 (2003).</mixed-citation><mixed-citation xml:lang="en">[EN03] P. Exner and K. Nˇemcov´a, Leaky quantum graphs: approximations by point-interaction Hamiltoni ans, J. Phys. A, 36, P. 10173–10193 (2003).</mixed-citation></citation-alternatives></ref><ref id="cit10"><label>10</label><citation-alternatives><mixed-citation xml:lang="ru">[LP08] M. Levitin and L. Parnovski, On the principal eigenvalue of a Robin problem with a large parameter, Math. Nachr., 281, P. 272–281 (2008).</mixed-citation><mixed-citation xml:lang="en">[LP08] M. Levitin and L. Parnovski, On the principal eigenvalue of a Robin problem with a large parameter, Math. Nachr., 281, P. 272–281 (2008).</mixed-citation></citation-alternatives></ref><ref id="cit11"><label>11</label><citation-alternatives><mixed-citation xml:lang="ru">[LLP10] I. Lobanov, V. Lotoreichik, and I.Yu. Popov, Lower bound on the spectrum of the two-dimensional Schr¨odinger operator with a delta-perturbation on a curve, Theor. Math. Phys., 162, P. 332–340 (2010).</mixed-citation><mixed-citation xml:lang="en">[LLP10] I. Lobanov, V. Lotoreichik, and I.Yu. Popov, Lower bound on the spectrum of the two-dimensional Schr¨odinger operator with a delta-perturbation on a curve, Theor. Math. Phys., 162, P. 332–340 (2010).</mixed-citation></citation-alternatives></ref><ref id="cit12"><label>12</label><citation-alternatives><mixed-citation xml:lang="ru">[M87] J. Marschall, The trace of Sobolev-Slobodeckij spaces on Lipschitz domains, Manuscripta Math., 58, P. 47–65 (1987).</mixed-citation><mixed-citation xml:lang="en">[M87] J. Marschall, The trace of Sobolev-Slobodeckij spaces on Lipschitz domains, Manuscripta Math., 58, P. 47–65 (1987).</mixed-citation></citation-alternatives></ref><ref id="cit13"><label>13</label><citation-alternatives><mixed-citation xml:lang="ru">[McL] W. McLean, Strongly elliptic systems and boundary integral equations. Cambridge University Press, Cambridge (2000)</mixed-citation><mixed-citation xml:lang="en">[McL] W. McLean, Strongly elliptic systems and boundary integral equations. Cambridge University Press, Cambridge (2000)</mixed-citation></citation-alternatives></ref></ref-list><fn-group><fn fn-type="conflict"><p>The authors declare that there are no conflicts of interest present.</p></fn></fn-group></back></article>
