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We identify a set of quantum graphs with unique and precisely defined spectral properties called {\it regular quantum graphs}. Although chaotic in their classical limit with positive topological entropy, regular quantum graphs are…

Quantum Physics · Physics 2009-11-07 R. Blümel , Yu. Dabaghian , R. V. Jensen

In this paper we will show that there does not exist a distance-regular graph $\Gamma$ with intersection array $\{80, 54,12; 1, 6, 60\}$. We first show that a local graph $\Delta$ of $\Gamma$ does not contain a coclique with 5 vertices, and…

Combinatorics · Mathematics 2018-09-27 Jack H. Koolen , Quaid Iqbal , Jongyook Park , Masood Ur Rehman

We pick up a solvable ${\cal PT}-$symmetric quantum square well on an interval of $x \in := (-L,L)\mathbb{G}^{(2)}$ (with an $\alpha-$dependent non-Hermiticity given by Robin boundary conditions) and generalize it. In essence, we just…

Quantum Physics · Physics 2013-01-15 Miloslav Znojil

The Erd\H{o}s-Simonovits stability theorem states that for all \epsilon >0 there exists \alpha >0 such that if G is a K_{r+1}-free graph on n vertices with e(G) > ex(n,K_{r+1}) - \alpha n^2, then one can remove \epsilon n^2 edges from G to…

Combinatorics · Mathematics 2022-05-03 József Balogh , Felix Christian Clemen , Mikhail Lavrov , Bernard Lidický , Florian Pfender

We give a simple proof based on symmetries that there are no geodesics from a vertex to itself in the cube, tetrahedron, octahedron, and icosahedron.

Dynamical Systems · Mathematics 2022-08-31 Serge Troubetzkoy

Fermat's Last Theorem (FLT) implies that the Frey curves do not exist. A proof of FLT independent of proved Taniyama-Shimura-Weil conjecture is presented.

General Mathematics · Mathematics 2013-07-22 Jailton C. Ferreira

In general relativity as well as gauge theories, non-trivial symmetries can appear at boundaries. In the presence of radiation some of the symmetries are not Hamiltonian vector fields, hence the definition of charges for the symmetries…

High Energy Physics - Theory · Physics 2025-03-26 Antoine Rignon-Bret , Simone Speziale

It was proved in [Y.-Q. Feng, C. H. Li and J.-X. Zhou, Symmetric cubic graphs with solvable automorphism groups, {\em European J. Combin.} {\bf 45} (2015), 1-11] that a cubic symmetric graph with a solvable automorphism group is either a…

Combinatorics · Mathematics 2016-07-12 Yan-Quan Feng , Klavdija Kutnar , Dragan Marusic , Da-Wei Yang

Let $\mathcal{G}$ be a quantum graph without quantum sources and $E_\mathcal{G}$ be the quantum edge correspondence for $\mathcal{G}.$ Our main results include sufficient conditions for simplicity of the Cuntz-Pimsner algebra…

Operator Algebras · Mathematics 2025-04-02 Mitch Hamidi , Lara Ismert , Brent Nelson

We outline some recent proofs of quantum ergodicity on large graphs and give new applications in the context of irregular graphs. We also discuss some remaining questions.

Spectral Theory · Mathematics 2019-02-01 Nalini Anantharaman , Mostafa Sabri

When all non-edge distances of a graph realized in $\mathbb{R}^{d}$ as a {\em bar-and-joint framework} are generically {\em implied} by the bar (edge) lengths, the graph is said to be {\em rigid} in $\mathbb{R}^{d}$. For $d=3$,…

Computational Geometry · Computer Science 2013-11-20 Jialong Cheng , Meera Sitharam , Ileana Streinu

We consider symmetric powers of a graph. In particular, we show that the spectra of the symmetric square of strongly regular graphs with the same parameters are equal. We also provide some bounds on the spectra of the symmetric squares of…

Combinatorics · Mathematics 2007-05-23 Koenraad Audenaert , Chris Godsil , Gordon Royle , Terry Rudolph

We present a conceptually new approach to describe state-of-the-art photonic quantum experiments using Graph Theory. There, the quantum states are given by the coherent superpositions of perfect matchings. The crucial observation is that…

Quantum Physics · Physics 2019-03-08 Xuemei Gu , Manuel Erhard , Anton Zeilinger , Mario Krenn

In this paper, we consider a sequence of open quantum graphs, with uniformly bounded data, and we are interested in the asymptotic distribution of their scattering resonances. Supposing that the number of leads in our quantum graphs is…

Spectral Theory · Mathematics 2022-05-11 Maxime Ingremeau

We prove that some well known compact quantum spaces like quantum tori and some quantum two-spheres do not admit a compact quantum group structure. This is achieved by considering existence of traces, characters and nuclearity of the…

Operator Algebras · Mathematics 2011-04-12 Piotr M. Soltan

Paths in an appropriate geometry are usually used as trajectories of test particles in geometric theories of gravity. It is shown that non-symmetric geometries possess some interesting quantum features. Without carrying out any quantization…

General Relativity and Quantum Cosmology · Physics 2015-06-25 M. I. Wanas , M. E. Kahil

We prove new lower bounds on the crossing number of a complete graphs assuming that it is drawn in such a way that it contains a Hamiltonian cycle with no crossings.

Combinatorics · Mathematics 2013-09-13 Daniel M. Kane

We investigate quantum graphs with infinitely many vertices and edges without the common restriction on the geometry of the underlying metric graph that there is a positive lower bound on the lengths of its edges. Our central result is a…

Mathematical Physics · Physics 2018-10-30 Pavel Exner , Aleksey Kostenko , Mark Malamud , Hagen Neidhardt

We initiate a systematic study of quantum properties of finite graphs, namely, quantum asymmetry, quantum symmetry, and quantum isomorphism. We define the Schmidt alternative for a class of graphs, which reveals to be a useful tool for…

Operator Algebras · Mathematics 2024-05-09 Paul Meunier

We construct a braided analogue of the quantum permutation group and show that it is the universal braided compact quantum group acting on a finite space in the category of $\mathbb{Z}/N\mathbb{Z}$-$\textrm{C}^*$-algebras with a twisted…

Quantum Algebra · Mathematics 2024-06-25 Anshu , Suvrajit Bhattacharjee , Atibur Rahaman , Sutanu Roy