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We introduce a class of pairs of graphs consisting of two cliques joined by an arbitrary number of edges. The members of a pair have the property that the clique-bridging edge-set of one graph is the complement of that of the other. We…

Combinatorics · Mathematics 2011-06-08 Adam Bohn

A graph is said to be symmetric if its automorphism group is transitive on its arcs. Guo et al. (Electronic J. Combin. 18, \#P233, 2011) and Pan et al. (Electronic J. Combin. 20, \#P36, 2013) determined all pentavalent symmetric graphs of…

Combinatorics · Mathematics 2017-02-21 Bo Ling , Ben Gong Lou , Ci Xuan Wu

In a number of recent works [6, 7] the authors have introduced and studied a functor $\mathcal{F}_k$ which associates to each loose graph $\Gamma$ -which is similar to a graph, but where edges with $0$ or $1$ vertex are allowed - a…

Algebraic Geometry · Mathematics 2016-11-24 Manuel Merida-Angulo , Koen Thas

For integer q>1, we derive edge q-colouring models for (i) the Tutte polynomial of a graph G on the hyperbola H_q, (ii) the symmetric weight enumerator of the set of group-valued q-flows of G, and (iii) a more general vertex colouring model…

Combinatorics · Mathematics 2007-07-17 Andrew J. Goodall

The {\it prime graph} $\Gamma(G)$ of a finite group $G$ is the graph whose vertex set is the set of prime divisors of $|G|$ and in which two distinct vertices $r$ and $s$ are adjacent if and only if there exists an element of $G$ of order…

Group Theory · Mathematics 2019-11-15 Ilya Gorshkov , Alexey Staroletov

A topological index of a graph $G$ is a real number which is preserved under isomorphism. Extensive studies on certain polynomials related to these topological indices have also been done recently. In a similar way, chromatic versions of…

General Mathematics · Mathematics 2018-11-02 Sudev Naduvath

Graph polynomials are graph parameters invariant under graph isomorphisms which take values in a polynomial ring with a fixed finite number of indeterminates. We study graph polynomials from a model theoretic point of view. In this paper we…

Logic · Mathematics 2018-05-24 J. A. Makowsky , E. V. Ravve , T. Kotek

We prove that, if $\Gamma$ is a finite connected $3$-valent vertex-transitive, or $4$-valent vertex- and edge-transitive graph, then either $\Gamma$ is part of a well-understood family of graphs, or every non-identity automorphism of…

Combinatorics · Mathematics 2024-12-20 Marco Barbieri , Valentina Grazian , Pablo Spiga

Symmetric edge polytopes are lattice polytopes associated with finite simple graphs that are of interest in both theory and applications. We investigate the facet structure of symmetric edge polytopes for various models of random graphs.…

Combinatorics · Mathematics 2024-02-14 Benjamin Braun , Kaitlin Bruegge , Matthew Kahle

There is a well-established dictionary between zonotopes, hyperplane arrangements, and their (oriented) matroids. Arguably one of the most famous examples is the class of graphical zonotopes, also called acyclotopes, which encode…

Combinatorics · Mathematics 2024-09-24 Eleonore Bach , Matthias Beck , Sophie Rehberg

Two linear recurrences exhibit mirror symmetry connecting the constants $e$ and $\pi$. When parametrized, their asymptotic connection constants extend to meromorphic functions satisfying additive functional equations with rational…

Number Theory · Mathematics 2026-01-09 Benoit Cloitre

Let $\Gamma$ be an Abelian group and let $G$ be a simple graph. We say that $G$ is $\Gamma$-colorable if for some fixed orientation of $G$ and every edge labeling $\ell:E(G)\rightarrow \Gamma$, there exists a vertex coloring $c$ by the…

Combinatorics · Mathematics 2023-12-05 Bartłomiej Bosek , Jarosław Grytczuk , Grzegorz Gutowski , Oriol Serra , Mariusz Zając

Given a finite group $G$, denote by $\Gamma(G)$ the simple undirected graph whose vertices are the distinct sizes of noncentral conjugacy classes of $G$, and set two vertices of $\Gamma(G)$ to be adjacent if and only if they are not coprime…

Group Theory · Mathematics 2013-06-10 Mariagrazia Bianchi , Rachel D. Camina , Marcel Herzog , Emanuele Pacifici

The symmetric edge polytope of a simple graph is a lattice polytope defined as the convex hull of a subset of the type A roots corresponding to the edges of the graph. In this article we prove a sharp lower bound for the number of edges of…

Combinatorics · Mathematics 2025-12-19 Giulia Codenotti , Roberto Riccardi , Lorenzo Venturello

We prove the connectedness and calculate the diameter of the oriented graph of graftings associated to exotic complex projective structures on a compact surface S with a given holonomy representation of Fuchsian type. The oriented graph of…

Geometric Topology · Mathematics 2014-01-22 Gabriel Calsamiglia , Bertrand Deroin , Stefano Francaviglia

The notion of a $\Gamma $-symmetric space is a generalization of the classical notion of a symmetric space, where a general finite abelian group $\Gamma $ replaces the group $Z_2$. The case $\Gamma =\Z_k$ has also been studied, from the…

Differential Geometry · Mathematics 2008-02-09 Yuri Bahturin , Michel Goze

In a series of papers the authors associated to an $L^2$-acyclic group $\Gamma$ an invariant $\mathcal{P}(\Gamma)$ that is a formal difference of polytopes in the vector space $H_1(\Gamma;\Bbb{R})$. This invariant is in particular defined…

Geometric Topology · Mathematics 2016-11-08 Stefan Friedl , Wolfgang Lück , Stephan Tillmann

Suppose a group $G$ acts properly on a simplicial complex $\Gamma$. Let $l$ be the number of $G$-invariant vertices and $p_1, p_2, ... p_m$ be the sizes of the $G$-orbits having size greater than 1. Then $\Gamma$ must be a subcomplex of…

Combinatorics · Mathematics 2008-12-25 Jonathan Browder

Given an underlying undirected simple graph, we consider the set of all acyclic orientations of its edges. Each of these orientations induces a partial order on the vertices of our graph and, therefore, we can count the number of linear…

Combinatorics · Mathematics 2015-02-17 Benjamin Iriarte Giraldo

In this note we obtain numerous new bases for the algebra of symmetric functions whose generators are chromatic symmetric functions. More precisely, if $\{ G_ k \}_{k\geq 1}$ is a set of connected graphs such that $G_k$ has $k$ vertices for…

Combinatorics · Mathematics 2016-08-31 Soojin Cho , Stephanie van Willigenburg