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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">10.17586/2220-8054-2017-8-2-216-230</article-id><article-id custom-type="elpub" pub-id-type="custom">najo-653</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>Unique continuation principles and their absence for Schrodinger eigenfunctions on combinatorial and quantum graphs and in continuum space</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>Peyerimhoff</surname><given-names>N.</given-names></name></name-alternatives><bio xml:lang="en"><p>Department of Mathematical Sciences</p></bio><email xlink:type="simple">norbert.peyerimhoff@durham.ac.uk</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>Taufer</surname><given-names>M.</given-names></name></name-alternatives><bio xml:lang="en"><p>Fakultat fur Mathematik</p></bio><email xlink:type="simple">mtaeufer@math.tu-dortmund.de</email><xref ref-type="aff" rid="aff-2"/></contrib><contrib contrib-type="author" corresp="yes"><name-alternatives><name name-style="western" xml:lang="en"><surname>Veselic</surname><given-names>I.</given-names></name></name-alternatives><bio xml:lang="en"><p>Fakultat fur Mathematik</p></bio><email xlink:type="simple">iveselic@math.tu-dortmund.de</email><xref ref-type="aff" rid="aff-2"/></contrib></contrib-group><aff-alternatives id="aff-1"><aff xml:lang="en">Durham University<country>United Kingdom</country></aff></aff-alternatives><aff-alternatives id="aff-2"><aff xml:lang="en">Technische Universitat Dortmund<country>Germany</country></aff></aff-alternatives><pub-date pub-type="collection"><year>2017</year></pub-date><pub-date pub-type="epub"><day>12</day><month>08</month><year>2025</year></pub-date><volume>8</volume><issue>2</issue><fpage>216</fpage><lpage>230</lpage><permissions><copyright-statement>Copyright &amp;#x00A9; Peyerimhoff N., Taufer M., Veselic I., 2025</copyright-statement><copyright-year>2025</copyright-year><copyright-holder xml:lang="ru">Peyerimhoff N., Taufer M., Veselic I.</copyright-holder><copyright-holder xml:lang="en">Peyerimhoff N., Taufer M., Veselic I.</copyright-holder><license 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/653">https://nanojournal.ifmo.ru/jour/article/view/653</self-uri><abstract><p>For the analysis of the Schrodinger and related equations it is of central importance whether a unique continuation principle (UCP) holds or not. In continuum Euclidean space, quantitative forms of unique continuation imply Wegner estimates and regularity properties of the integrated density of states (IDS) of Schrodinger operators with random potentials. For discrete Schr odinger equations on the lattice, only a weak analog of the UCP holds, but it is sufficient to guarantee the continuity of the IDS. For other combinatorial graphs, this is no longer true. Similarly, for quantum graphs the UCP does not hold in general and consequently, the IDS does not need to be continuous.</p></abstract><kwd-group xml:lang="en"><kwd>eigenfunctions</kwd><kwd>unique continuation</kwd><kwd>Schrodinger equation</kwd><kwd>Wegner estimate</kwd><kwd>Integrated density of states.</kwd></kwd-group><funding-group xml:lang="en"><funding-statement>This work was partially financially supported by the Deutsche Forschungsgemeinschaft through the grants VE 253/6-1 Unique continuation principles and equidistribution properties of eigenfunctions and VE 253/7-1 Multiscale version of the Logvinenko-Sereda Theorem. While writing part of this article, NP and MT enjoyed the hospitality of the Isaac Newton Institute during the programme Non-Positive Curvature Group Actions and Cohomology, supported by the EPSRC Grant EP/K032208/1. We would like to thank Michela Egidi for reading a previous version of the manuscript</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">Bourgain J. and Kenig C. E. On localization in the continuous Anderson-Bernoulli model in higher dimension. Invent. Math., 2005, 161(2), P. 389–426.</mixed-citation><mixed-citation xml:lang="en">Bourgain J. and Kenig C. E. On localization in the continuous Anderson-Bernoulli model in higher dimension. Invent. Math., 2005, 161(2), P. 389–426.</mixed-citation></citation-alternatives></ref><ref id="cit2"><label>2</label><citation-alternatives><mixed-citation xml:lang="ru">Carleman T. Sur un probleme d’unicite pour les systemes d’equations aux derivees partielles a deux variables independantes. ´Ark. Mat. Astron. Fysik, 1939, 26B(17), P. 1–9.</mixed-citation><mixed-citation xml:lang="en">Carleman T. Sur un probleme d’unicite pour les systemes d’equations aux derivees partielles a deux variables independantes. ´Ark. Mat. Astron. Fysik, 1939, 26B(17), P. 1–9.</mixed-citation></citation-alternatives></ref><ref id="cit3"><label>3</label><citation-alternatives><mixed-citation xml:lang="ru">Kenig C.E., Ruiz A., and Sogge C.D. Uniform Sobolev inequalities and unique continuation for second order constant coefficient differential operators. Duke Math. J., 1987, 55, P. 329–347.</mixed-citation><mixed-citation xml:lang="en">Kenig C.E., Ruiz A., and Sogge C.D. Uniform Sobolev inequalities and unique continuation for second order constant coefficient differential operators. Duke Math. J., 1987, 55, P. 329–347.</mixed-citation></citation-alternatives></ref><ref id="cit4"><label>4</label><citation-alternatives><mixed-citation xml:lang="ru">Koch H. and Tataru D. Carleman estimates and unique continuation for second-order elliptic equations with nonsmooth coefficients. Comm. Pure Appl. Math., 2001, 54(3), P. 339–360.</mixed-citation><mixed-citation xml:lang="en">Koch H. and Tataru D. Carleman estimates and unique continuation for second-order elliptic equations with nonsmooth coefficients. Comm. Pure Appl. Math., 2001, 54(3), P. 339–360.</mixed-citation></citation-alternatives></ref><ref id="cit5"><label>5</label><citation-alternatives><mixed-citation xml:lang="ru">Wolff T. H. Note on counterexamples in strong unique continuation problems. Proc. Amer. Math. Soc., 1992, 114(2), P. 351–356.</mixed-citation><mixed-citation xml:lang="en">Wolff T. H. Note on counterexamples in strong unique continuation problems. Proc. Amer. Math. Soc., 1992, 114(2), P. 351–356.</mixed-citation></citation-alternatives></ref><ref id="cit6"><label>6</label><citation-alternatives><mixed-citation xml:lang="ru">Wolff T. H. Recent work on sharp estimates in second order elliptic unique continuation problems. In Fourier analysis and partial differential equations (Miraflores de la Sierra, 1992), Stud. Adv. Math., pages 99–128. CRC, Boca Raton, FL, 1995.</mixed-citation><mixed-citation xml:lang="en">Wolff T. H. Recent work on sharp estimates in second order elliptic unique continuation problems. In Fourier analysis and partial differential equations (Miraflores de la Sierra, 1992), Stud. Adv. Math., pages 99–128. CRC, Boca Raton, FL, 1995.</mixed-citation></citation-alternatives></ref><ref id="cit7"><label>7</label><citation-alternatives><mixed-citation xml:lang="ru">Escauriaza L., Kenig C. E., Ponce G. and Vega L. Uniqueness properties of solutions to Schrodinger equations. Bull. Amer. Math. Soc. (N.S.), 2012, 49(3), P. 415–442.</mixed-citation><mixed-citation xml:lang="en">Escauriaza L., Kenig C. E., Ponce G. and Vega L. Uniqueness properties of solutions to Schrodinger equations. Bull. Amer. Math. Soc. (N.S.), 2012, 49(3), P. 415–442.</mixed-citation></citation-alternatives></ref><ref id="cit8"><label>8</label><citation-alternatives><mixed-citation xml:lang="ru">Jerison D. and Kenig C.E. Unique continuation and absence of positive eigenvalues for Schrodinger operators. Ann. of Math. (2), 1985, 121(3), P. 463–494. With an appendix by E. M. Stein.</mixed-citation><mixed-citation xml:lang="en">Jerison D. and Kenig C.E. Unique continuation and absence of positive eigenvalues for Schrodinger operators. Ann. of Math. (2), 1985, 121(3), P. 463–494. With an appendix by E. M. Stein.</mixed-citation></citation-alternatives></ref><ref id="cit9"><label>9</label><citation-alternatives><mixed-citation xml:lang="ru">Donnelly H. and Fefferman C. Nodal sets of eigenfunctions on Riemannian manifolds. Invent. math., 1988, 93(1), P. 161–183.</mixed-citation><mixed-citation xml:lang="en">Donnelly H. and Fefferman C. Nodal sets of eigenfunctions on Riemannian manifolds. Invent. math., 1988, 93(1), P. 161–183.</mixed-citation></citation-alternatives></ref><ref id="cit10"><label>10</label><citation-alternatives><mixed-citation xml:lang="ru">Bakri L. Carleman estimates for the Schrodinger operator. Applications to quantitative uniqueness. ¨ Commun. Part. Diff. Eq., 2013, 38(1), P. 69–91.</mixed-citation><mixed-citation xml:lang="en">Bakri L. Carleman estimates for the Schrodinger operator. Applications to quantitative uniqueness. ¨ Commun. Part. Diff. Eq., 2013, 38(1), P. 69–91.</mixed-citation></citation-alternatives></ref><ref id="cit11"><label>11</label><citation-alternatives><mixed-citation xml:lang="ru">Germinet F. and Klein A. A comprehensive proof of localization for continuous Anderson models with singular random potentials. J. Eur. Math. Soc., 2013, 15(1), P. 53–143.</mixed-citation><mixed-citation xml:lang="en">Germinet F. and Klein A. A comprehensive proof of localization for continuous Anderson models with singular random potentials. J. Eur. Math. Soc., 2013, 15(1), P. 53–143.</mixed-citation></citation-alternatives></ref><ref id="cit12"><label>12</label><citation-alternatives><mixed-citation xml:lang="ru">Stollmann P. Caught by disorder: Bound States in Random Media, volume 20 of Progress in Mathematical Physics. Birkhauser, 2001.</mixed-citation><mixed-citation xml:lang="en">Stollmann P. Caught by disorder: Bound States in Random Media, volume 20 of Progress in Mathematical Physics. Birkhauser, 2001.</mixed-citation></citation-alternatives></ref><ref id="cit13"><label>13</label><citation-alternatives><mixed-citation xml:lang="ru">Carmona R.,Klein A., and Martinelli F. Anderson localization for Bernoulli and other singular potentials. Commun. Math. Phys., 1987, 108, P. 41–66.</mixed-citation><mixed-citation xml:lang="en">Carmona R.,Klein A., and Martinelli F. Anderson localization for Bernoulli and other singular potentials. Commun. Math. Phys., 1987, 108, P. 41–66.</mixed-citation></citation-alternatives></ref><ref id="cit14"><label>14</label><citation-alternatives><mixed-citation xml:lang="ru">Bourgain J. and Klein A. Bounds on the density of states for Schrodinger operators. Invent. Math., 2013, 194(1), P. 41–72</mixed-citation><mixed-citation xml:lang="en">Bourgain J. and Klein A. Bounds on the density of states for Schrodinger operators. Invent. Math., 2013, 194(1), P. 41–72</mixed-citation></citation-alternatives></ref><ref id="cit15"><label>15</label><citation-alternatives><mixed-citation xml:lang="ru">Craig W. and Simon B. Subharmonicity of the Lyaponov index. Duke Math. J., 1983, 50(2), P. 551–560.</mixed-citation><mixed-citation xml:lang="en">Craig W. and Simon B. Subharmonicity of the Lyaponov index. Duke Math. J., 1983, 50(2), P. 551–560.</mixed-citation></citation-alternatives></ref><ref id="cit16"><label>16</label><citation-alternatives><mixed-citation xml:lang="ru">Meshkov V.Z. On the possible rate of decay at infinity of solutions of second order partial differential equations. Math. USSR Sb., 1992, 72(2), P. 343–361.</mixed-citation><mixed-citation xml:lang="en">Meshkov V.Z. On the possible rate of decay at infinity of solutions of second order partial differential equations. Math. USSR Sb., 1992, 72(2), P. 343–361.</mixed-citation></citation-alternatives></ref><ref id="cit17"><label>17</label><citation-alternatives><mixed-citation xml:lang="ru">Rojas-Molina C. and Veselic I. Scale-free unique continuation estimates and application to random Schrodinger operators. Commun. Math. Phys., 2013, 320(1), P. 245–274.</mixed-citation><mixed-citation xml:lang="en">Rojas-Molina C. and Veselic I. Scale-free unique continuation estimates and application to random Schrodinger operators. Commun. Math. Phys., 2013, 320(1), P. 245–274.</mixed-citation></citation-alternatives></ref><ref id="cit18"><label>18</label><citation-alternatives><mixed-citation xml:lang="ru">Germinet F., Muller P., and Rojas-Molina C. Ergodicity and dynamical localization for Delone-Anderson operators. Rev. Math. Phys., 2015, 27(9), P. 1550020,36.</mixed-citation><mixed-citation xml:lang="en">Germinet F., Muller P., and Rojas-Molina C. Ergodicity and dynamical localization for Delone-Anderson operators. Rev. Math. Phys., 2015, 27(9), P. 1550020,36.</mixed-citation></citation-alternatives></ref><ref id="cit19"><label>19</label><citation-alternatives><mixed-citation xml:lang="ru">Combes J.-M., Hislop P. D., and Klopp F. Holder continuity of the integrated density of states for some random operators at all energies. Int. Math. Res. Not., 2003, 4, P. 179–209.</mixed-citation><mixed-citation xml:lang="en">Combes J.-M., Hislop P. D., and Klopp F. Holder continuity of the integrated density of states for some random operators at all energies. Int. Math. Res. Not., 2003, 4, P. 179–209.</mixed-citation></citation-alternatives></ref><ref id="cit20"><label>20</label><citation-alternatives><mixed-citation xml:lang="ru">Combes J.-M., Hislop P. D., and Klopp F. An optimal Wegner estimate and its application to the global continuity of the integrated density of states for random Schrodinger operators. ¨ Duke Math. J., 2007, 140(3), P. 469–498.</mixed-citation><mixed-citation xml:lang="en">Combes J.-M., Hislop P. D., and Klopp F. An optimal Wegner estimate and its application to the global continuity of the integrated density of states for random Schrodinger operators. ¨ Duke Math. J., 2007, 140(3), P. 469–498.</mixed-citation></citation-alternatives></ref><ref id="cit21"><label>21</label><citation-alternatives><mixed-citation xml:lang="ru">Klein A. Unique continuation principle for spectral projections of Schrodinger operators and optimal Wegner estimates for non-ergodic random Schrodinger operators. Commun. Math. Phys., 2013, 323(3), P. 1229–1246.</mixed-citation><mixed-citation xml:lang="en">Klein A. Unique continuation principle for spectral projections of Schrodinger operators and optimal Wegner estimates for non-ergodic random Schrodinger operators. Commun. Math. Phys., 2013, 323(3), P. 1229–1246.</mixed-citation></citation-alternatives></ref><ref id="cit22"><label>22</label><citation-alternatives><mixed-citation xml:lang="ru">Nakic I., Taufer M., Tautenhahn M., and Veselic I. Scale-free uncertainty principles and Wegner estimates for random breather ´potentials. C. R. Math., 2015, 353(10), P. 919–923.</mixed-citation><mixed-citation xml:lang="en">Nakic I., Taufer M., Tautenhahn M., and Veselic I. Scale-free uncertainty principles and Wegner estimates for random breather ´potentials. C. R. Math., 2015, 353(10), P. 919–923.</mixed-citation></citation-alternatives></ref><ref id="cit23"><label>23</label><citation-alternatives><mixed-citation xml:lang="ru">Nakic I., Taufer M., Tautenhahn M., and Veselic I. Scale-free unique continuation principle, eigenvalue lifting and Wegnerestimates for random Schrodinger operators. arXiv:1609.01953 [math.AP], 2016.</mixed-citation><mixed-citation xml:lang="en">Nakic I., Taufer M., Tautenhahn M., and Veselic I. Scale-free unique continuation principle, eigenvalue lifting and Wegnerestimates for random Schrodinger operators. arXiv:1609.01953 [math.AP], 2016.</mixed-citation></citation-alternatives></ref><ref id="cit24"><label>24</label><citation-alternatives><mixed-citation xml:lang="ru">Taufer M. and VeselicI. Conditional Wegner estimate for the standard random breather potential. ´ J. Stat. Phys., 2015, 161(4), P. 902–914. arXiv:1509.03507.</mixed-citation><mixed-citation xml:lang="en">Taufer M. and VeselicI. Conditional Wegner estimate for the standard random breather potential. ´ J. Stat. Phys., 2015, 161(4), P. 902–914. arXiv:1509.03507.</mixed-citation></citation-alternatives></ref><ref id="cit25"><label>25</label><citation-alternatives><mixed-citation xml:lang="ru">Shirley C. Decorrelation estimates for some continuous and discrete random Schrodinger operators in dimension one, without covering condition. 2015. https://hal.archives-ouvertes.fr/hal-01149320</mixed-citation><mixed-citation xml:lang="en">Shirley C. Decorrelation estimates for some continuous and discrete random Schrodinger operators in dimension one, without covering condition. 2015. https://hal.archives-ouvertes.fr/hal-01149320</mixed-citation></citation-alternatives></ref><ref id="cit26"><label>26</label><citation-alternatives><mixed-citation xml:lang="ru">Le Rousseau J. and Lebeau G. On Carleman estimates for elliptic and parabolic operators. Applications to unique continuation and control of parabolic equations. ESAIM Contr. Optim. Ca., 2012, 18(3), P. 712–747.</mixed-citation><mixed-citation xml:lang="en">Le Rousseau J. and Lebeau G. On Carleman estimates for elliptic and parabolic operators. Applications to unique continuation and control of parabolic equations. ESAIM Contr. Optim. Ca., 2012, 18(3), P. 712–747.</mixed-citation></citation-alternatives></ref><ref id="cit27"><label>27</label><citation-alternatives><mixed-citation xml:lang="ru">Delyon F. and Souillard B. Remark on the continuity of the density of states of ergodic finite-difference operators. Commun. Math. Phys., 1984, 94, P. 289–291.</mixed-citation><mixed-citation xml:lang="en">Delyon F. and Souillard B. Remark on the continuity of the density of states of ergodic finite-difference operators. Commun. Math. Phys., 1984, 94, P. 289–291.</mixed-citation></citation-alternatives></ref><ref id="cit28"><label>28</label><citation-alternatives><mixed-citation xml:lang="ru">Wegner F. Bounds on the density of states in disordered systems. Z. Phys. B, 1981, 44, P. 9–15.</mixed-citation><mixed-citation xml:lang="en">Wegner F. Bounds on the density of states in disordered systems. Z. Phys. B, 1981, 44, P. 9–15.</mixed-citation></citation-alternatives></ref><ref id="cit29"><label>29</label><citation-alternatives><mixed-citation xml:lang="ru">Craig W. and Simon B. Log Holder continuity of the integrated density of states for stochastic Jacobi matrices. Commun. Math. Phys., 1983, 90, P. 207–218.</mixed-citation><mixed-citation xml:lang="en">Craig W. and Simon B. Log Holder continuity of the integrated density of states for stochastic Jacobi matrices. Commun. Math. Phys., 1983, 90, P. 207–218.</mixed-citation></citation-alternatives></ref><ref id="cit30"><label>30</label><citation-alternatives><mixed-citation xml:lang="ru">Veselic I. Spectral analysis of percolation Hamiltonians. ´ Math. Ann., 2005, 331(4), P. 841–865. http://arXiv.org/math-ph/0405006.</mixed-citation><mixed-citation xml:lang="en">Veselic I. Spectral analysis of percolation Hamiltonians. ´ Math. Ann., 2005, 331(4), P. 841–865. http://arXiv.org/math-ph/0405006.</mixed-citation></citation-alternatives></ref><ref id="cit31"><label>31</label><citation-alternatives><mixed-citation xml:lang="ru">Chayes J. T., Chayes L., Franz J. R., Sethna J. P., and Trugman S. A. On the density of states for the quantum percolation problem. J. Phys. A, 1986, 19(18), P. L1173–L1177.</mixed-citation><mixed-citation xml:lang="en">Chayes J. T., Chayes L., Franz J. R., Sethna J. P., and Trugman S. A. On the density of states for the quantum percolation problem. J. Phys. A, 1986, 19(18), P. L1173–L1177.</mixed-citation></citation-alternatives></ref><ref id="cit32"><label>32</label><citation-alternatives><mixed-citation xml:lang="ru">Antunovic T. and Veseli ´ c I. Spectral asymptotics of percolation Hamiltonians on amenable Cayley graphs. Volume 186 of ´Operator Theory: Advances and Applications, pages 1–29. Birkhauser, 2008. http://arxiv.org/abs/0707.4292.</mixed-citation><mixed-citation xml:lang="en">Antunovic T. and Veseli ´ c I. Spectral asymptotics of percolation Hamiltonians on amenable Cayley graphs. Volume 186 of ´Operator Theory: Advances and Applications, pages 1–29. Birkhauser, 2008. http://arxiv.org/abs/0707.4292.</mixed-citation></citation-alternatives></ref><ref id="cit33"><label>33</label><citation-alternatives><mixed-citation xml:lang="ru">Lenz D. and Veselic I. Hamiltonians on discrete structures: jumps of the integrated density of states and uniform convergence. ´ Math. Z., 2009, 263(4), P. 813–835.</mixed-citation><mixed-citation xml:lang="en">Lenz D. and Veselic I. Hamiltonians on discrete structures: jumps of the integrated density of states and uniform convergence. ´ Math. Z., 2009, 263(4), P. 813–835.</mixed-citation></citation-alternatives></ref><ref id="cit34"><label>34</label><citation-alternatives><mixed-citation xml:lang="ru">Schumacher Ch., Schwarzenberger F., and VeselicI. A Glivenko–Cantelli theorem for almost additive functions on lattices. Stoch. Proc. Appl, 2016, 127(1), P. 179–208. https://arxiv.org/abs/1606.07664.</mixed-citation><mixed-citation xml:lang="en">Schumacher Ch., Schwarzenberger F., and VeselicI. A Glivenko–Cantelli theorem for almost additive functions on lattices. Stoch. Proc. Appl, 2016, 127(1), P. 179–208. https://arxiv.org/abs/1606.07664.</mixed-citation></citation-alternatives></ref><ref id="cit35"><label>35</label><citation-alternatives><mixed-citation xml:lang="ru">Chaudhury R.P., Chu C.W., Galstyan E., Galstyan E., Lorenz B., Sun Y.Y., Wang Y.Q., and Yen F. Magnetic phase diagrams of the kagom?? staircase compound. Physica B: Condensed Matter, 2008, 403(5-9), P. 1487–1489. Proceedings of the International Conference on Strongly Correlated Electron Systems.</mixed-citation><mixed-citation xml:lang="en">Chaudhury R.P., Chu C.W., Galstyan E., Galstyan E., Lorenz B., Sun Y.Y., Wang Y.Q., and Yen F. Magnetic phase diagrams of the kagom?? staircase compound. Physica B: Condensed Matter, 2008, 403(5-9), P. 1487–1489. Proceedings of the International Conference on Strongly Correlated Electron Systems.</mixed-citation></citation-alternatives></ref><ref id="cit36"><label>36</label><citation-alternatives><mixed-citation xml:lang="ru">Lawes G., Harris A.B., Kimura T., Rogado N., Cava R.J., Aharony A., Entin-Wohlman O., Yildirim T., Kenzelmann M., Broholm C., and Ramirez A.P. Magnetically driven ferroelectric order in ni3v2o8. Phys. Rev. Lett., 2005, 95(Aug), P. 087205.</mixed-citation><mixed-citation xml:lang="en">Lawes G., Harris A.B., Kimura T., Rogado N., Cava R.J., Aharony A., Entin-Wohlman O., Yildirim T., Kenzelmann M., Broholm C., and Ramirez A.P. Magnetically driven ferroelectric order in ni3v2o8. Phys. Rev. Lett., 2005, 95(Aug), P. 087205.</mixed-citation></citation-alternatives></ref><ref id="cit37"><label>37</label><citation-alternatives><mixed-citation xml:lang="ru">Helffer B., Kerdelhue P., and Royo-Letelier J. Chambers’s formula for the graphene and the Hou model with kagome periodicity ´ and applications. Ann. Henri Poincare´, 2016, 17(4), P. 795–818.</mixed-citation><mixed-citation xml:lang="en">Helffer B., Kerdelhue P., and Royo-Letelier J. Chambers’s formula for the graphene and the Hou model with kagome periodicity ´ and applications. Ann. Henri Poincare´, 2016, 17(4), P. 795–818.</mixed-citation></citation-alternatives></ref><ref id="cit38"><label>38</label><citation-alternatives><mixed-citation xml:lang="ru">Hou J.M. Light-induced hofstadter’s butterfly spectrum of ultracold atoms on the two-dimensional kagome lattice. Chinese Physics Letters, 2009, 26(12), P. 123701.</mixed-citation><mixed-citation xml:lang="en">Hou J.M. Light-induced hofstadter’s butterfly spectrum of ultracold atoms on the two-dimensional kagome lattice. Chinese Physics Letters, 2009, 26(12), P. 123701.</mixed-citation></citation-alternatives></ref><ref id="cit39"><label>39</label><citation-alternatives><mixed-citation xml:lang="ru">Kerdelhue P. and Royo-Letelier J. On the low lying spectrum of the magnetic Schr ´ odinger operator with kagome periodicity. Rev. Math. Phys., 2014, 26(10), P. 1450020,46.</mixed-citation><mixed-citation xml:lang="en">Kerdelhue P. and Royo-Letelier J. On the low lying spectrum of the magnetic Schr ´ odinger operator with kagome periodicity. Rev. Math. Phys., 2014, 26(10), P. 1450020,46.</mixed-citation></citation-alternatives></ref><ref id="cit40"><label>40</label><citation-alternatives><mixed-citation xml:lang="ru">Lenz D., Peyerimhoff N., Post O., and Veselic I. Continuity of the integrated density of states on random length metric graphs. ´Math. Phys. Anal. Geom., 2009, 12(3), P. 219–254.</mixed-citation><mixed-citation xml:lang="en">Lenz D., Peyerimhoff N., Post O., and Veselic I. Continuity of the integrated density of states on random length metric graphs. ´Math. Phys. Anal. Geom., 2009, 12(3), P. 219–254.</mixed-citation></citation-alternatives></ref><ref id="cit41"><label>41</label><citation-alternatives><mixed-citation xml:lang="ru">Baues O. and Peyerimhoff N. Geodesics in non-positively curved plane tessellations. Adv. Geom., 2006, 6(2), P. 243–263.</mixed-citation><mixed-citation xml:lang="en">Baues O. and Peyerimhoff N. Geodesics in non-positively curved plane tessellations. Adv. Geom., 2006, 6(2), P. 243–263.</mixed-citation></citation-alternatives></ref><ref id="cit42"><label>42</label><citation-alternatives><mixed-citation xml:lang="ru">Klassert S., Lenz D., Peyerimhoff N., and Stollmann P. Elliptic operators on planar graphs: unique continuation for eigenfunctions and nonpositive curvature. Proc. Amer. Math. Soc., 2006, 134(5), P. 1549–1559.</mixed-citation><mixed-citation xml:lang="en">Klassert S., Lenz D., Peyerimhoff N., and Stollmann P. Elliptic operators on planar graphs: unique continuation for eigenfunctions and nonpositive curvature. Proc. Amer. Math. Soc., 2006, 134(5), P. 1549–1559.</mixed-citation></citation-alternatives></ref><ref id="cit43"><label>43</label><citation-alternatives><mixed-citation xml:lang="ru">Keller M. Curvature, geometry and spectral properties of planar graphs. Discrete Computational. Geom., 2011, 46(3), P. 500–525.</mixed-citation><mixed-citation xml:lang="en">Keller M. Curvature, geometry and spectral properties of planar graphs. Discrete Computational. Geom., 2011, 46(3), P. 500–525.</mixed-citation></citation-alternatives></ref><ref id="cit44"><label>44</label><citation-alternatives><mixed-citation xml:lang="ru">Keller M., Peyerimhoff N., and Pogorzelski F. Sectional curvature of polygonal complexes with planar substructures. arXiv:1407.4024 [math.MG], 2015.</mixed-citation><mixed-citation xml:lang="en">Keller M., Peyerimhoff N., and Pogorzelski F. Sectional curvature of polygonal complexes with planar substructures. arXiv:1407.4024 [math.MG], 2015.</mixed-citation></citation-alternatives></ref><ref id="cit45"><label>45</label><citation-alternatives><mixed-citation xml:lang="ru">Cattaneo C. The spectrum of the continuous Laplacian on a graph. Monatsh. Math., 1997, 124(3), P. 215–235.</mixed-citation><mixed-citation xml:lang="en">Cattaneo C. The spectrum of the continuous Laplacian on a graph. Monatsh. Math., 1997, 124(3), P. 215–235.</mixed-citation></citation-alternatives></ref><ref id="cit46"><label>46</label><citation-alternatives><mixed-citation xml:lang="ru">Pankrashkin K. Spectra of Schrodinger operators on equilateral quantum graphs. ¨ Lett. Math. Phys., 2006, 77(2), P. 139–154.</mixed-citation><mixed-citation xml:lang="en">Pankrashkin K. Spectra of Schrodinger operators on equilateral quantum graphs. ¨ Lett. Math. Phys., 2006, 77(2), P. 139–154.</mixed-citation></citation-alternatives></ref><ref id="cit47"><label>47</label><citation-alternatives><mixed-citation xml:lang="ru">Post O. Equilateral quantum graphs and boundary triples. In Analysis on graphs and its applications, volume 77 of Proc. Sympos. Pure Math., pages 469–490. Amer. Math. Soc., Providence, RI, 2008.</mixed-citation><mixed-citation xml:lang="en">Post O. Equilateral quantum graphs and boundary triples. In Analysis on graphs and its applications, volume 77 of Proc. Sympos. Pure Math., pages 469–490. Amer. Math. Soc., Providence, RI, 2008.</mixed-citation></citation-alternatives></ref><ref id="cit48"><label>48</label><citation-alternatives><mixed-citation xml:lang="ru">Lledo F. and Post O. Eigenvalue bracketing for discrete and metric graphs. ´ J. Math. Anal. Appl., 2008, 348(2), P. 806–833.</mixed-citation><mixed-citation xml:lang="en">Lledo F. and Post O. Eigenvalue bracketing for discrete and metric graphs. ´ J. Math. Anal. Appl., 2008, 348(2), P. 806–833.</mixed-citation></citation-alternatives></ref><ref id="cit49"><label>49</label><citation-alternatives><mixed-citation xml:lang="ru">J. von Below. A characteristic equation associated to an eigenvalue problem on c 2 -networks. Linear Algebra Appl., 1985, 71, P. 309–325.</mixed-citation><mixed-citation xml:lang="en">J. von Below. A characteristic equation associated to an eigenvalue problem on c 2 -networks. Linear Algebra Appl., 1985, 71, P. 309–325.</mixed-citation></citation-alternatives></ref><ref id="cit50"><label>50</label><citation-alternatives><mixed-citation xml:lang="ru">Klopp F. and Pankrashkin K. Localization on quantum graphs with random edge lengths. Lett. Math. Phys., 2009, 87(1-2), P. 99–114.</mixed-citation><mixed-citation xml:lang="en">Klopp F. and Pankrashkin K. Localization on quantum graphs with random edge lengths. Lett. Math. Phys., 2009, 87(1-2), P. 99–114.</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>
