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Let $X$ and $Y$ be two graphs of order $n$. The friends-and-strangers graph $\textup{FS}(X,Y)$ of $X$ and $Y$ is a graph whose vertex set consists of all bijections $\sigma: V(X)\rightarrow V(Y)$, in which two bijections $\sigma$ and $…

Combinatorics · Mathematics 2025-04-02 Xinghui Zhao , Lihua You , Jifu Lin , Xiaoxue Zhang

For a connected graph $G$ and $X\subseteq V(G)$, we say that two vertices $u$, $v$ are $X$-visible if there is a shortest $u,v$-path $P$ with $V(P)\cap X \subseteq \{u,v\}$. If every two vertices from $X$ are $X$-visible, then $X$ is a…

Combinatorics · Mathematics 2025-05-27 Pakanun Dokyeesun , Csilla Bujtás

A simple generalization of the Hall's condition in bipartite graphs, the Normalized Matching Property (NMP) in a graph $G(X,Y,E)$ with vertex partition $(X,Y)$ states that for any subset $S\subseteq X$, we have…

Combinatorics · Mathematics 2021-06-25 Niranjan Balachandran , Deepanshu Kush

Bounds are proved for the connective constant \mu\ of an infinite, connected, \Delta-regular graph G. The main result is that \mu\ \ge \sqrt{\Delta-1} if G is vertex-transitive and simple. This inequality is proved subject to weaker…

Combinatorics · Mathematics 2013-05-02 Geoffrey R. Grimmett , Zhongyang Li

We derive attainable upper bounds on the algebraic connectivity (spectral gap) of a regular graph in terms of its diameter and girth. This bound agrees with the well-known Alon-Boppana-Friedman bound for graphs of even diameter, but is an…

Combinatorics · Mathematics 2023-07-17 Geoffrey Exoo , Theodore Kolokolnikov , Jeanette Janssen , Timothy Salamon

Given $n$-vertex simple graphs $X$ and $Y$, the friends-and-strangers graph $\mathsf{FS}(X, Y)$ has as its vertices all $n!$ bijections from $V(X)$ to $V(Y)$, where two bijections are adjacent if and only if they differ on two adjacent…

Combinatorics · Mathematics 2023-12-20 Ryan Jeong

We find conditions for the connectivity of inhomogeneous random graphs with intermediate density. Our results generalize the classical result for G(n, p), when p = c log n/n. We draw n independent points X_i from a general distribution on a…

Probability · Mathematics 2012-10-25 Luc Devroye , Nicolas Fraiman

We address a system of weakly interacting particles where the heterogenous connections among the particles are described by a graph sequence and the number of particles grows to infinity. Our results extend the existing law of large numbers…

Probability · Mathematics 2025-06-03 Fabio Coppini , Anna De Crescenzo , Huyen Pham

We say that a metric graph is uniformly bounded if the degrees of all vertices are uniformly bounded and the lengths of edges are pinched between two positive constants; a metric space is approximable by a uniform graph if there is one…

Metric Geometry · Mathematics 2013-06-25 Dmitri Burago , Sergei Ivanov

In this paper we investigate the $directed$ $normalizing$ $graph$ associated with a group $G$, defined as the simple directed graph whose vertices are the elements of $G$, with an arrow from $x$ to $y$ whenever the subgroup $\langle x…

Group Theory · Mathematics 2025-11-04 Costantino Delizia , Michele Gaeta , Carmine Monetta

We consider the count of subgraphs with an arbitrary configuration of endpoints in the random-connection model based on a Poisson point process on ${\Bbb R}^d$. We present combinatorial expressions for the computation of the cumulants and…

Probability · Mathematics 2025-07-02 Qingwei Liu , Nicolas Privault

When each vertex is assigned a set, the intersection graph generated by the sets is the graph in which two distinct vertices are joined by an edge if and only if their assigned sets have a nonempty intersection. An interval graph is an…

Combinatorics · Mathematics 2017-02-13 Jeong Han Kim , Sang June Lee , Joohan Na

Let $G$ denote a $Q$-polynomial distance-regular graph with diameter $D$ at least 4. Assume that the intersection numbers of $G$ satisfy $a_i=0$ for $0 \leq i \leq D-1$ and $a_D\neq 0$. We show that $G$ is a polygon, a folded cube, or an…

Combinatorics · Mathematics 2016-09-07 Michael S. Lang , Paul M. Terwilliger

The unit ball random geometric graph $G=G^d_p(\lambda,n)$ has as its vertices $n$ points distributed independently and uniformly in the $d$-dimensional unit ball, with two vertices adjacent if and only if their $l_p$-distance is at most…

Combinatorics · Mathematics 2011-10-05 Robert B. Ellis , Jeremy L. Martin , Catherine Yan

We generalize the notion of quasirandom which concerns a class of equivalent properties that random graphs satisfy. We show that the convergence of a graph sequence under the spectral distance is equivalent to the convergence using the…

Combinatorics · Mathematics 2013-11-06 Fan Chung

We introduce a natural generalization of the Erd\H{o}s-R\'enyi random graph model in which random instances of a fixed motif are added independently. The binomial random motif graph $G(H,n,p)$ is the random (multi)graph obtained by adding…

Combinatorics · Mathematics 2019-07-30 Michael Anastos , Peleg Michaeli , Samantha Petti

A graph is called $d$-rigid if there exists a generic embedding of its vertex set into $\mathbb{R}^d$ such that every continuous motion of the vertices that preserves the lengths of all edges actually preserves the distances between all…

Combinatorics · Mathematics 2023-12-13 Michael Krivelevich , Alan Lew , Peleg Michaeli

In this paper, we study the connectivity of a one-dimensional soft random geometric graph (RGG). The graph is generated by placing points at random on a bounded line segment and connecting pairs of points with a probability that depends on…

Probability · Mathematics 2021-01-04 Michael Wilsher , Carl P. Dettmann , Ayalvadi Ganesh

We give a unified approach to analysing, for each positive integer $s$, a class of finite connected graphs that contains all the distance transitive graphs as well as the locally $s$-arc transitive graphs of diameter at least $s$. A graph…

Combinatorics · Mathematics 2010-10-29 Alice Devillers , Michael Giudici , Cai Heng Li , Cheryl E. Praeger

We consider a finite-dimensional, locally finite CAT(0) cube complex X admitting a co-compact properly discontinuous countable group of automorphisms G. We construct a natural compact metric space B(X) on which G acts by homeomorphisms, the…

Geometric Topology · Mathematics 2011-05-10 Amos Nevo , Michah Sageev
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