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Consider the graph $\mathbb{H}(d)$ whose vertex set is the hyperbolic plane, where two points are connected with an edge when their distance is equal to some $d>0$. Asking for the chromatic number of this graph is the hyperbolic analogue to…

Combinatorics · Mathematics 2019-06-04 Evan DeCorte , Konstantin Golubev

Let $G$ be a connected graph with maximum degree $\Delta \ge 3$. We investigate the upper bound for the chromatic number $\chi_\gamma(G)$ of the power graph $G^\gamma$. It was proved that $\chi_\gamma(G)…

Combinatorics · Mathematics 2014-10-07 Lian-Ying Miao , Yi-Zheng Fan

Coloring a graph $G$ consists in finding an assignment of colors $c: V(G)\to\{1,\ldots,p\}$ such that any pair of adjacent vertices receives different colors. The minimum integer $p$ such that a coloring exists is called the chromatic…

Discrete Mathematics · Computer Science 2019-12-25 Théo Pierron

We consider unavoidable chromatic patterns in $2$-colorings of the edges of the complete graph. Several such problems are explored being a junction point between Ramsey theory, extremal graph theory (Tur\'an type problems), zero-sum Ramsey…

Combinatorics · Mathematics 2019-04-09 Yair Caro , Adriana Hansberg , Amanda Montejano

We propose the spectral degree exponent as a novel graph metric. Although Hofmeister \cite{HofmeisterThesis} has studied the same metric, we generalise Hofmeister's work to weighted graphs. We provide efficient iterative formulas and bounds…

Combinatorics · Mathematics 2025-02-05 Massimo A. Achterberg , Piet Van Mieghem

The adjacency operator of a graph has a spectrum and a class of scalar-valued spectral measures which have been systematically analyzed; it also has a spectral multiplicity function which has been less studied. The first purpose of this…

Combinatorics · Mathematics 2024-03-06 Pierre de la Harpe

The topological Tverberg theorem has been generalized in several directions by setting extra restrictions on the Tverberg partitions. Restricted Tverberg partitions, defined by the idea that certain points cannot be in the same part, are…

Combinatorics · Mathematics 2013-11-06 Alexander Engström , Patrik Norén

This paper is devoted to the study of the conformal spectrum (and more precisely the first eigenvalue) of the Laplace-Beltrami operator on a smooth connected compact Riemannian surface without boundary, endowed with a conformal class. We…

Differential Geometry · Mathematics 2014-07-29 Nikolai Nadirashvili , Yannick Sire

We define a (pseudo-)distance between graphs based on the spectrum of the normalized Laplacian, which is easy to compute or to estimate numerically. It can therefore serve as a rough classification of large empirical graphs into families…

Spectral Theory · Mathematics 2019-04-03 Jiao Gu , Jürgen Jost , Shiping Liu , Peter F. Stadler

We establish an Expander Mixing Lemma for directed graphs in terms of the eigenvalues of an associated asymmetric transition probability matrix, extending the classical spectral inequality to the asymmetric setting. As an application, we…

Combinatorics · Mathematics 2025-11-04 Rebecca Carter

The classical Stein-Tomas restriction theorem is equivalent to the statement that the spectral measure $dE(\lambda)$ of the square root of the Laplacian on $\RR^n$ is bounded from $L^p(\RR^n)$ to $L^{p'}(\RR^n)$ for $1 \leq p \leq…

Analysis of PDEs · Mathematics 2012-05-02 Colin Guillarmou , Andrew Hassell , Adam Sikora

We consider a family of compact manifolds which shrinks with respect to an appropriate parameter to a graph. The main result is that the spectrum of the Laplace-Beltrami operator converges to the spectrum of the (differential) Laplacian on…

Mathematical Physics · Physics 2020-01-30 Pavel Exner , Olaf Post

Given $0<\alpha\leq\pi$, ${\epsilon}>0$ and $n$, we define random graphs on the $d$-dimensional sphere by drawing $n$ i.i.d. uniform random points for the vertices, and edges $u {\sim} v$ whenever the geodesic distance between $u$ and $v$…

Combinatorics · Mathematics 2022-07-29 Francisco Martinez-Figueroa

We consider magnetic Schroedinger operators on quantum graphs with identical edges. The spectral problem for the quantum graph is reduced to the discrete magnetic Laplacian on the underlying combinatorial graph and a certain Hill operator.…

Mathematical Physics · Physics 2007-05-23 Konstantin Pankrashkin

Deep neural networks have been applied to a wide range of problems across different application domains with great success. Recently, research into combinatorial optimization problems in particular has generated much interest in the machine…

Machine Learning · Computer Science 2021-08-05 Jason Van Hulse , Joshua S. Friedman

The classical Andr\'{a}sfai-Erd\H{o}s-S\'{o}s theorem considers the chromatic number of $K_{r + 1}$-free graphs with large minimum degree, and in the case $r = 2$ says that any $n$-vertex triangle-free graph with minimum degree greater than…

Combinatorics · Mathematics 2023-08-22 Freddie Illingworth

I prove that the spectrum of the Laplace-Beltrami operator with the Neumann boundary condition on a compact Riemannian manifold with boundary admits a fast approximation by the spectra of suitable graph Laplacians on proximity graphs on the…

Differential Geometry · Mathematics 2019-11-21 Jinpeng Lu

In this paper we address sampling and approximation of functions on combinatorial graphs. We develop filtering on graphs by using Schr\"odinger's group of operators generated by combinatorial Laplace operator. Then we construct a sampling…

Information Theory · Computer Science 2011-11-28 Isaac Z. Pesenson , Meyer Z. Pesenson

This paper is a study of ``topological'' lower bounds for the chromatic number of a graph. Such a lower bound was first introduced by Lov\'asz in 1978, in his famous proof of the \emph{Kneser conjecture} via Algebraic Topology. This…

Combinatorics · Mathematics 2007-05-23 Jiri Matousek , Günter M. Ziegler

Elek and Lippner (2010) showed that the convergence of a sequence of bounded-degree graphs implies the existence of a limit for the proportion of vertices covered by a maximum matching. We provide a characterization of the limiting…

Probability · Mathematics 2012-04-12 Charles Bordenave , Marc Lelarge , Justin Salez