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We show that almost all circulant graphs have automorphism groups as small as possible. Of the circulant graphs that do not have automorphism group as small as possible, we give some families of integers such that it is not true that almost…

Combinatorics · Mathematics 2012-03-06 Soumya Bhoumik , Edward Dobson , Joy Morris

We call an oriented odd cycle alternating if it has exactly one vertex whose in-degree and out-degree are both positive. In this paper, we investigate whether certain graphs admit an orientation that avoids alternating odd cycles as…

Combinatorics · Mathematics 2025-08-27 Nóra Almási , Gábor Simonyi

For an integer $k\geq 1$, a graph is called a $k$-circulant if its automorphism group contains a cyclic semiregular subgroup with $k$ orbits on the vertices. We show that, if $k$ is even, there exist infinitely many cubic arc-transitive…

Combinatorics · Mathematics 2016-03-07 Michael Giudici , István Kovács , Cai Heng Li , Gabriel Verret

The majority of graphs whose sandpile groups are known are either regular or simple. We give an explicit formula for a family of non-regular multi-graphs called thick cycles. A thick cycle graph is a cycle where multi-edges are permitted.…

An $acyclic$ edge coloring of a graph is a proper edge coloring such that there are no bichromatic cycle s. The \emph{acyclic chromatic index} of a graph is the minimum number k such that there is an acyclic e dge coloring using k colors…

Combinatorics · Mathematics 2008-10-20 Manu Basavaraju , L. Sunil Chandran

A consistent path system in a graph $G$ is an intersection-closed collection of paths, with exactly one path between any two vertices in $G$. We call $G$ metrizable if every consistent path system in it is the system of geodesic paths…

Combinatorics · Mathematics 2023-11-17 Maria Chudnovsky , Daniel Cizma , Nati Linial

If $H$ is (or is isomorphic to) a subgraph of $G$, $H$ is said to {\it divide} $G$ if there is an edge-decomposition of $G$ by copies of $E(H)$, the edge set of $H$. A more restrictive version of this is when there is a subgroup ${\cal H}$…

Combinatorics · Mathematics 2013-09-06 Michel Mollard , Mark Ramras

Let $M\circ N$ denote the Schur product of two matrices $M$ and $N$. A graph $X$ with adjacency matrix $A$ is walk regular if $A^k\circ I$ is a constant times $I$ for each $k\ge0$, and $X$ is 1-walk-regular if it is walk regular and…

Combinatorics · Mathematics 2025-01-28 Chris Godsil , Wanting Sun , Xiaohong Zhang

An arc of a graph is an oriented edge and a 3-arc is a 4-tuple $(v,u,x,y)$ of vertices such that both $(v,u,x)$ and $(u,x,y)$ are paths of length two. The 3-arc graph of a graph $G$ is defined to have vertices the arcs of $G$ such that two…

Combinatorics · Mathematics 2013-11-14 Guangjun Xu , Sanming Zhou

In this paper, we investigate a family of graphs associated to collections of arcs on surfaces. These {\it multiarc graphs} naturally interpolate between arc graphs and flip graphs, both well studied objects in low dimensional geometry and…

Geometric Topology · Mathematics 2019-03-01 Hugo Parlier , Ashley Weber

Universal cycles, such as De Bruijn cycles, are cyclic sequences of symbols that represent every combinatorial object from some family exactly once as a consecutive subsequence. Graph universal cycles are a graph analogue of universal…

Combinatorics · Mathematics 2023-08-14 Rachel Kirsch , Clare Sibley , Elizabeth Sprangel

A CIS graph is a graph in which every maximal stable set and every maximal clique intersect. A graph is well-covered if all its maximal stable sets are of the same size, co-well-covered if its complement is well-covered, and…

Combinatorics · Mathematics 2016-08-08 Edward Dobson , Ademir Hujdurović , Martin Milanič , Gabriel Verret

It is shown that Euler's theorem for graphs can be generalized for 2-complexes. Two notions that generalize cycle and Eulerian tour are introduced (``circlet'' and ``Eulerian cover''), and we show that for a strongly-connected, pure…

Combinatorics · Mathematics 2024-01-02 Richard H. Hammack , Paul C. Kainen

If $\Gamma$ is a graph for which every edge is in exactly one clique of order $\omega$, then one can form a new graph with vertex set equal to these cliques. This is a generalization of the line graph of $\Gamma$. We discover many general…

Combinatorics · Mathematics 2026-05-25 Connor Phillips

We introduce a new model for investigating spectral properties of quantum graphs, a quantum circulant graph. Circulant graphs are the Cayley graphs of cyclic groups. Quantum circulant graphs with standard vertex conditions maintain…

Mathematical Physics · Physics 2019-06-21 JM Harrison , E Swindle

It is well-known that every vertex-transitive graph admits a representation as a coset graph. In this paper, we extend this construction by introducing monodromy graphs defined through double cosets. Our main result establishes that every…

Combinatorics · Mathematics 2025-09-23 Kai Yuan , Yan Wang

Following Alspach and Parsons, a {\em metacirculant graph} is a graph admitting a transitive group generated by two automorphisms $\rho$ and $\sigma$, where $\rho$ is $(m,n)$-semiregular for some integers $m \geq 1$, $n \geq 2$, and where…

Combinatorics · Mathematics 2007-05-23 Dragan Marusic , Primoz Sparl

By a map we mean a $2$-cell decomposition of a closed compact surface, i.e., an embedding of a graph such that every face is homeomorphic to an open disc. Automorphism of a map can be thought of as a permutation of the vertices which…

Combinatorics · Mathematics 2021-01-08 Ken-ichi Kawarabayashi , Bojan Mohar , Roman Nedela , Peter Zeman

In this paper, we characterise the family of finite arc-transitive bicirculants. We show that every finite arc-transitive bicirculant is a normal $r$-cover of an arc-transitive graph that lies in one of eight infinite families or is one of…

Combinatorics · Mathematics 2022-01-25 Alice Devillers , Michael Giudici , Wei Jin

This paper presents a solution of the polycirculant conjecture which states that every vertex-transitive graph G has an automorphism that permutes the vertices in cycles of the same length. This is done by identifying vertex-transitive…

Combinatorics · Mathematics 2007-05-23 Eric Mwambene