Abstract
It is known that up to certain pathologies, a compact metric graph with standard vertex conditions has a Baire-generic set of choices of edge lengths such that all Laplacian eigenvalues are simple and have eigenfunctions that do not vanish at the vertices, [16, 12]. We provide a new notion of strong genericity, using subanalytic sets, that implies both Baire genericity and full Lebesgue measure. We show that the previous genericity results for metric graphs are strongly generic. In addition, we show that generically the derivative of an eigenfunction does not vanish at the vertices either. In fact, we show that generically an eigenfunction fails to satisfy any additional vertex condition. Finally, we show that any two different metric graphs with the same edge lengths do not share any non-zero eigenvalue, for a generic choice of lengths, except for a few explicit cases where the graphs have a common edge-reflection symmetry. The paper concludes by addressing three open conjectures for metric graphs that can benefit from the tools introduced in this paper.
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References
J. Agler, J. E. McCarthy and M. Stankus, Toral algebraic sets and function theory on polydisks, J. Geom. Anal. 16 (2006), 551–562.
J. H. Albert, Topology of the Nodal and Critical Point Sets for Eigenfunctions of Elliptic Operators, Ph.D. Thesis, Massachusetts Institute of Technology, Cambridge, MA, 1971.
L. Alon, Quantum graphs-generic eigenfunctions and their nodal Count and Neumann count statistics, arXiv:2010.03004 [math-ph].
L. Alon, R. Band and G. Berkolaiko, Nodal statistics on Quantum graphs, Comm. Math. Phys. 362 (2018), 909–948.
L. Alon, R. Band and G. Berkolaiko, Universality of nodal count distribution in large metric graphs, Exp. Math. (2022), 1–35.
R. Band, G. Berkolaiko and T. Weyand, Anomalous nodal count and singularities in the dispersion relation of honeycomb graphs, J. Math. Phys. 56 (2015), Article no. 122111.
R. Band and G. Lévy, Quantum graphs which optimize the spectral gap, Ann. Henri Poincaré 18 (2017), 3269–3323.
F. Barra and P. Gaspard, On the level spacing distribution in quantum graphs, J. Statist. Phys. 101 (2000), 283–319.
G. Berkolaiko, A lower bound for nodal count on discrete and metric graphs, Comm. Math. Phys. 278 (2008), 803–819.
G. Berkolaiko and P. Kuchment, Introduction to Quantum Graphs, American Mathematical Society, Providence, RI, 2013.
G. Berkolaiko, Y. Latushkin and S. Sukhtaiev, Limits of quantum graph operators with shrinking edges, Adv. Math. 352 (2019), 632–669.
G. Berkolaiko and W. Liu, Simplicity of eigenvalues and non-vanishing of eigenfunctions of a quantum graph, J. Math. Anal. Appl. 445 (2017), 803–818.
G. Berkolaiko and B. Winn, Relationship between scattering matrix and spectrum of quantum graphs, Trans. Amer. Math. Soc. 362 (2010), 6261–6277.
E. Bierstone and P. D. Milman, Semianalytic and subanalytic sets, Inst. Hautes Etudes Sci. Publ. Math. 67 (1988), 5–42.
Y. Colin de Verdière, Semi-classical measures on quantum graphs and the Gauß map of the determinant manifold, Ann. Henri Poincaré 16 (2015), 347–364.
L. Friedlander, Genericity of simple eigenvalues for a metric graph, Israel J. Math. 146 (2005), 149–156.
A. M. Gabriélov, Projections of semi-analytic sets, Funct. Anal. Appl. 2 (1968), 282–291.
S. Gnutzmann, J. P. Keating and F. Piotet, Eigenfunction statistics on quantum graphs, Ann. Physics 325 (2010), 2595–2640.
S. Gnutzmann and U. Smilansky, Quantum graphs: Applications to quantum chaos and universal spectral statistics, Adv. Phys. 55 (2006), 527–625.
S. Gnutzmann, U. Smilansky and J. Weber, Nodal counting on quantum graphs, Waves Random Media 14 (2004), S61–S73.
B. Gutkin and U. Smilansky, Can one hear the shape of a graph?, J. Phys. A 34 (2001), 6061–6068.
L. Hillairet and C. Judge, Generic spectral simplicity of polygons, Proc. Amer. Math. Soc. 137 (2009), 2139–2145.
L. Hillairet and C. Judge, Hyperbolic triangles without embedded eigenvalues, Ann. of Math. (2) 187 (2018), 301–377.
M. Hofmann, J. B. Kennedy, D. Mugnolo and M. Plümer, On pleijel’s nodal domain theorem for quantum graphs, Ann. Henri Poincaré 22 (2021), 3841–3870.
T. Kottos and U. Smilansky, Quantum chaos on graphs, Phys. Rev. Lett. 79 (1997), 4794–4797.
P. Kurasov, Spectral Geometry of Graphs, Birkhäuser, Berlin–Heidelberg, 2023.
P. Kurasov and M. Nowaczyk, Inverse spectral problem for quantum graphs, J. Phys. A 38 (2005), 4901–4915.
P. Kurasov and P. Sarnak, Stable polynomials and crystalline measures, J. Math. Phys. 61 (2020), Article no. 083501.
P. Kurasov and P. Sarnak, The additive structure of the spectrum of the laplacian on a metric graph, in preparation.
M. Plümer and M. Täufer, On fully supported eigenfunctions of quantum graphs, Lett. Math. Phys. 111 (2021), Article no. 153.
K. Uhlenbeck, Eigenfunctions of Laplace operators, Bull. Amer. Math. Soc. 78 (1972), 1073–1076.
L. Van den Dries and C. Miller, Geometric categories and o-minimal structures, Duke Math. J. 84 (1996), pp. 497–540.
Acknowledgments
The author would like to thank Peter Sarnak, Mark Goresky, Karen Uhlenbeck, Pavel Kurasov, and Ram Band for insightful discussions, important remarks and relevant references. The author was supported by the Ambrose Monell Foundation and the Institute for Advanced Study.
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Alon, L. Generic Laplacian eigenfunctions on metric graphs. JAMA (2023). https://doi.org/10.1007/s11854-023-0308-x
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DOI: https://doi.org/10.1007/s11854-023-0308-x