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This paper presents a characterization of edge-transitive graphs which are four regular and have girth four. This class consists of four infinite families plus four exceptional graphs.

Combinatorics · Mathematics 2015-11-24 Tomas Boothby , Matt DeVos

We investigate connected cubic vertex-transitive graphs whose edge sets admit a partition into a $2$-factor $\mathcal{C}$ and a $1$-factor that is invariant under a vertex-transitive subgroup of the automorphism group of the graph and where…

Combinatorics · Mathematics 2026-01-19 Brian Alspach , Primoz Sparl

In this paper, we examine the structure of vertex- and edge-transitive strongly regular graphs, using normal quotient reduction. We show that the irreducible graphs in this family have quasiprimitive automorphism groups, and prove (using…

Combinatorics · Mathematics 2009-07-10 Joy Morris , Cheryl E. Praeger , Pablo Spiga

A graph is called {\em arc-transitive} (or {\em symmetric}) if its automorphism group has a single orbit on ordered pairs of adjacent vertices, and 2-arc-transitive its automorphism group has a single orbit on ordered paths of length 2. In…

Group Theory · Mathematics 2014-09-30 Marston D. E. Conder , Cai-Heng Li , Primoz Potocnik

A graph Gamma is said to be 2-arc-transitive if its full automorphism group Aut(\Gamma) has a single orbit on ordered paths of length 2, and for G\leq Aut(\Gamma), \Gamma is G-regular if G is regular on the vertex set of \Gamma. Let G be a…

Group Theory · Mathematics 2017-01-06 Jia-Li Du , Yan-Quan Feng

Nut graphs are graphs whose adjacency matrix is singular with one-dimensional null space spanned by a vector with no zero entries. In a recent paper, Ba\v{s}i\'c, Fowler and Pisanski proved that the automorphism group of a nut graph has…

Combinatorics · Mathematics 2025-08-26 Ksenija Rozman , Primož Šparl

We prove that, given a finite graph $\Sigma$ satisfying some mild conditions, there exist infinitely many tetravalent half-arc-transitive normal covers of $\Sigma$. Applying this result, we establish the existence of infinite families of…

Combinatorics · Mathematics 2020-11-25 Pablo Spiga , Binzhou Xia

A graph $\Gamma$ is $G$-symmetric if $G$ is a group of automorphisms of $\Gamma$ which is transitive on the set of ordered pairs of adjacent vertices of $\Gamma$. If $V(\Gamma)$ admits a nontrivial $G$-invariant partition ${\cal B}$ such…

Combinatorics · Mathematics 2019-08-06 Yu Qing Chen , Teng Fang , Sanming Zhou

A graph $\Gamma$ is $G$-symmetric if it admits $G$ as a group of automorphisms acting transitively on the set of arcs of $\Gamma$, where an arc is an ordered pair of adjacent vertices. Let $\Gamma$ be a $G$-symmetric graph such that its…

Combinatorics · Mathematics 2024-03-05 Teng Fang , Sanming Zhou , Shenglin Zhou

A non-complete graph $\Gamma$ is said to be $(G,2)$-distance transitive if $G$ is a subgroup of the automorphism group of $\Gamma$ that is transitive on the vertex set of $\Gamma$, and for any vertex $u$ of $\Gamma$, the stabilizer $G_u$ is…

Group Theory · Mathematics 2015-07-07 Brian P. Corr , Wei Jin , Csaba Schneider

Let ${\cal M}$ be a map with the underlying graph $\Gamma$. The automorphism group $Aut({\cal M})$ induces a natural action on the set of all vertex-edge-face incident triples, called {\em flags} of ${\cal M}$. The map ${\cal M}$ is said to…

Combinatorics · Mathematics 2017-08-04 Isabel Hubard , Alejandra Ramos-Rivera , Primož Šparl

In this paper, we introduce a family of tetravalent graphs called propeller graphs, denoted by $Pr_{n}(b,c,d)$. We then produce three infinite subfamilies and one finite subfamily of arc-transitive propeller graphs, and show that all such…

Combinatorics · Mathematics 2016-01-05 Matthew C. Sterns

We analyse the normal quotient structure of several infinite families of finite connected edge-transitive, four-valent oriented graphs. These families were singled out by Marusic and others to illustrate various different internal…

Combinatorics · Mathematics 2016-12-21 Jehan A. Al-bar , Ahmad N. Al-kenani , Najat Mohammad Muthana , Cheryl E. Praeger

We determine all factorisations $X=AB$, where $X$ is a finite almost simple group and $A,B$ are core-free subgroups such that $A\cap B$ is cyclic or dihedral. As a main application, we classify the graphs $\Gamma$ admitting an almost simple…

Group Theory · Mathematics 2024-05-24 Martin W. Liebeck , Cheryl E. Praeger

A graph $\Gamma$ is a bi-Cayley graph over a group $G$ if $G$ is a semiregular group of automorphisms of $\Gamma$ having two orbits. Let $G$ be a non-abelian metacyclic $p$-group for an odd prime $p$, and let $\Gamma$ be a connected…

Combinatorics · Mathematics 2017-07-11 Yi Wang , Yan-Quan Feng

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

We construct the first infinite families of locally arc transitive graphs with the property that the automorphism group has two orbits on vertices and is quasiprimitive on exactly one orbit, of twisted wreath type. This work contributes to…

Combinatorics · Mathematics 2022-03-01 Eda Kaja , Luke Morgan

A graph is said to be $k$-{\em isoregular} if any two vertex subsets of cardinality at most $k$, that induce subgraphs of the same isomorphism type, have the same number of neighbors. It is shown that no $3$-isoregular bicirculant (and more…

Combinatorics · Mathematics 2025-01-31 Klavdija Kutnar , Dragan Marušič , Štefko Miklavič

A graph $\Gamma = (V,E)$ of order $n$ is {\em distance magic} if it admits a bijective labeling $\ell \colon V \to \{1,2, \ldots, n\}$ of its vertices for which there exists a positive integer $\kappa$ such that $\sum_{u \in N(v)} \ell(u) =…

Combinatorics · Mathematics 2024-12-09 Štefko Miklavič , Primož Šparl

The intention of the paper is to move a step towards a classification of network topologies that exhibit periodic quantum dynamics. We show that the evolution of a quantum system, whose hamiltonian is identical to the adjacency matrix of a…

Quantum Physics · Physics 2007-05-23 Nitin Saxena , Simone Severini , Igor Shparlinski