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A graph $G$ is a prime distance graph (respectively, a 2-odd graph) if its vertices can be labeled with distinct integers such that for any two adjacent vertices, the difference of their labels is prime (either 2 or odd). We prove that…

Combinatorics · Mathematics 2021-06-07 Joshua D. Laison , Colin Starr , Andrea Walker

By a finite type-graph we mean a graph whose set of vertices is the set of all $k$-subsets of $[n]=\{1,2,\ldots, n\}$ for some integers $n\ge k\ge 1$, and in which two such sets are adjacent if and only if they realise a certain order type…

Combinatorics · Mathematics 2017-09-12 Christian Avart , Bill Kay , Christian Reiher , Vojtěch Rödl

Applying a method of Godsil and McKay \cite{GM} to some graphs related to the symplectic graph, a series of new infinite families of strongly regular graphs with parameters…

Combinatorics · Mathematics 2016-05-25 Alice M. W. Hui , Bernardo Rodrigues

Let $G$ be a group. The directed endomorphism graph, $\dend(G)$ of $G$ is a directed graph with vertex set $G$ and there is a directed edge from the vertex $a$ to the vertex $b$ if $a \neq b$ and there exists an endomorphism on $G$ mapping…

Group Theory · Mathematics 2025-11-20 Midhuna V Ajith , Peter J Cameron , Mainak Ghosh , Aparna Lakshmanan S

A finite graph $\Gamma$ is called $G$-symmetric if $G$ is a group of automorphisms of $\Gamma$ which is transitive on the set of ordered pairs of adjacent vertices of $\Gamma$. We study a family of symmetric graphs, called the unitary…

Combinatorics · Mathematics 2015-03-25 Massimo Giulietti , Stefano Marcugini , Fernanda Pambianco , Sanming Zhou

The spectrum of the $k$-power hypergraph of a graph $G$ is called the $k$-ordered spectrum of $G$.If graphs $G_1$ and $G_2$ have same $k$-ordered spectrum for all positive integer $k\geq2$, $G_1$ and $G_2$ are said to be high-ordered…

Combinatorics · Mathematics 2021-11-09 Lixiang Chen , Lizhu Sun , Changjiang Bu

The interplay between groups and graphs have been the most famous and productive area of algebraic graph theory. In this paper, we introduce and study the graphs whose vertex set is group G such that two distinct vertices a and b having…

Combinatorics · Mathematics 2019-01-01 Shafiq Ur Rehman , Abdul Qudair Baig , Muhammad Imran , Zia Ullah Khan

Let $G$ be a group. The directed endomorphism graph, \dend of $G$ is a directed graph with vertex set $G$ and there is a directed edge from the vertex `$a$' to the vertex `$\, b$' $(a \neq b) $ if and only if there exists an endomorphism on…

Combinatorics · Mathematics 2025-12-16 Midhuna V Ajith , Mainak Ghosh , Aparna Lakshmanan S

The distinguishing number of a permutation group $G\leqslant\Sym(\Omega)$ is the minimum number of colours needed to colour $\Omega$ in such a way that the only colour preserving element of $G$ is the identity. The distinguishing number of…

Combinatorics · Mathematics 2026-01-23 Lei Chen , Alice Devillers , Luke Morgan , Friedrich Rober

Let G be a simple, finite, connected, and undirected graph. The middle graph M(G) of G is obtained from the subdivision graph S(G) after joining pairs of subdivided vertices that lie on adjacent edges of G and the central graph C(G) of G is…

Combinatorics · Mathematics 2026-04-09 Amitayu Banerjee , Alexa Gopaulsingh , Zalán Molnár

A graph $G$ is said to be the intersection of graphs $G_1,G_2,\ldots,G_k$ if $V(G)=V(G_1)=V(G_2)=\cdots=V(G_k)$ and $E(G)=E(G_1)\cap E(G_2)\cap\cdots\cap E(G_k)$. For a graph $G$, $\mathrm{dim}_{COG}(G)$ (resp. $\mathrm{dim}_{TH}(G)$)…

Discrete Mathematics · Computer Science 2020-01-06 Daphna Chacko , Mathew C. Francis

There has been a great deal of attention recently to graphs whose vertex set is a group, defined using the group structure. (The commuting graph, where two elements are joined if they commute, is the oldest and most famous example.) The…

Combinatorics · Mathematics 2026-02-03 Peter J. Cameron

A graph $G$ is asymmetric if its automorphism group of vertices is trivial. Asymmetric graphs were introduced by Erd\H{o}s and R\'{e}nyi in 1963 where they measured the degree of asymmetry of an asymmetric graph. They proved that any…

Combinatorics · Mathematics 2020-07-23 Alejandra Brewer , Adam Gregory , Quindel Jones , Darren A. Narayan

Assume $G$ is a graph. We view $G$ as a symmetric digraph, in which each edge $uv$ of $G$ is replaced by a pair of opposite arcs $e=(u,v)$ and $e^{-1}=(v,u)$. Assume $S$ is an inverse closed subset of permutations of positive integers. We…

Combinatorics · Mathematics 2019-08-07 Ligang Jin , Tsai-Lien Wong , Xuding Zhu

A graph $\G$ is {\em symmetric} or {\em arc-transitive} if its automorphism group $\Aut(\G)$ is transitive on the arc set of the graph, and $\G$ is {\em basic} if $\Aut(\G)$ has no non-trivial normal subgroup $N$ such that the quotient…

Combinatorics · Mathematics 2017-07-18 Da-Wei Yang , Yan-Quan Feng , Jin Ho Kwak , Jaeun Lee

An interval $k$-graph is the intersection graph of a family $\mathcal{I}$ of intervals of the real line partitioned into at most $k$ classes with vertices adjacent if and only if their corresponding intervals intersect and belong to…

Combinatorics · Mathematics 2016-03-01 David E. Brown , Breeann M. Flesch , Larry J. Langley

A vertex triple $(u,v,w)$ of a graph is called a $2$-geodesic if $v$ is adjacent to both $u$ and $w$ and $u$ is not adjacent to $w$. A graph is said to be $2$-geodesic transitive if its automorphism group is transitive on the set of…

Combinatorics · Mathematics 2022-07-28 Jun-Jie Huang , Yan-Quan Feng , Jin-Xin Zhou , Fu-Gang Yin

A half-square of a bipartite graph $B=(X,Y,E_B)$ has one color class of $B$ as vertex set, say $X$; two vertices are adjacent whenever they have a common neighbor in $Y$. If $G=(V,E_G)$ is the half-square of a planar bipartite graph…

Discrete Mathematics · Computer Science 2018-12-12 Hoang-Oanh Le , Van Bang Le

For a graph $G$, a vertex subset $S$ is called a maximum generalized $k$-independent set if the induced subgraph $G[S]$ does not contain a $k$-tree as its subgraph, and the subset has maximum cardinality. The generalized $k$-independence…

Combinatorics · Mathematics 2025-09-15 Jing Huang

The complete transposition graph is defined to be the graph whose vertices are the elements of the symmetric group $S_n$, and two vertices $\alpha$ and $\beta$ are adjacent in this graph iff there is some transposition $(i,j)$ such that…

Combinatorics · Mathematics 2015-12-11 Ashwin Ganesan