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A graph is (m, k)-colourable if its vertices can be coloured with m colours such that the maximum degree of any subgraph induced on ver- tices receiving the same colour is at most k. The k-defective chromatic number for a graph is the least…

Combinatorics · Mathematics 2015-01-20 Nirmala Achuthan , N. R. Achuthan , G. Keady

A triangle-free graph $G$ is called read-$k$ when there exists a monotone Boolean formula $\phi$ whose variables are the vertices of $G$ and whose minterms are precisely the edges of $G$, such that no variable occurs more than $k$ times in…

Combinatorics · Mathematics 2007-05-23 Martin Charles Golumbic , Uri N. Peled , Udi Rotics

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 $k$-regular graph of girth $g$ is called edge-girth-regular graph, shortly egr-graph, if each of its edges is contained in exactly $\lambda$ distinct $g-$cycles. An egr-graph is called extremal for the triple $(k, g, \lambda)$ if has the…

Combinatorics · Mathematics 2024-01-30 Gabriela Araujo-Pardo , György Kiss , István Porupsánszki

A connected graph of order $n$ admitting a semiregular automorphism of order $n/k$ is called a $k$-multicirculant. Highly symmetric multicirculants of small valency have been extensively studied, and several classification results exist for…

Combinatorics · Mathematics 2022-08-15 Primož Potočnik , Micael Toledo

In this paper we define cycle-star graph CSk,n-k to be a graph on n vertices consisting of the cycle of length k and n-k leafs appended to the same vertex of the cycle. Also, we define cycle-path graph CPk,n-k to be a graph on n vertices…

Combinatorics · Mathematics 2013-06-19 Jelena Sedlar

A cycle double cover (CDC) of an undirected graph is a collection of the graph's cycles such that every edge of the graph belongs to exactly two cycles. We describe a constructive method for generating all the cubic graphs that have a 6-CDC…

Discrete Mathematics · Computer Science 2009-04-17 Rodrigo S. C. Leao , Valmir C. Barbosa

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

For a set of nonnegative integers $c_1, \ldots, c_k$, a $(c_1, c_2,\ldots, c_k)$-coloring of a graph $G$ is a partition of $V(G)$ into $V_1, \ldots, V_k$ such that for every $i$, $1\le i\le k, G[V_i]$ has maximum degree at most $c_i$. We…

Combinatorics · Mathematics 2018-06-21 Heather Hoskins , Runrun Liu , Jennifer Vandenbussche , Gexin Yu

The characterization of distance-regular Cayley graphs originated from the problem of identifying strongly regular Cayley graphs, or equivalently, regular partial difference sets. In this paper, a classification of distance-regular Cayley…

Combinatorics · Mathematics 2022-03-25 Xueyi Huang , Kinkar Chandra Das , Lu Lu

Let $k$ and $l$ be integers, both at least 2. A $(k,l)$-bipartite graph is an $l$-regular bipartite multigraph with coloured bipartite sets of size $k$. Define $\chi(k,l)$ and $\mu(k,l)$ to be the minimum and maximum order of automorphism…

Combinatorics · Mathematics 2025-10-06 Peter J. Cameron , Coen del Valle , Colva M. Roney-Dougal

A graph is $H$-free if it has no induced subgraph isomorphic to $H$. Brandst\"adt, Engelfriet, Le and Lozin proved that the class of chordal graphs with independence number at most 3 has unbounded clique-width. Brandst\"adt, Le and Mosca…

Discrete Mathematics · Computer Science 2015-09-29 Andreas Brandstädt , Konrad K. Dabrowski , Shenwei Huang , Daniël Paulusma

In this paper, we introduce the concept of $k$-integral graphs. A graph $\Gamma$ is called $k$-integral if the extension degree of the splitting field of the characteristic polynomial of $\Gamma$ over rational field $\mathbb Q$ is equal to…

Combinatorics · Mathematics 2025-08-06 Alireza Abdollahi , Majid Arezoomand , Tao Feng , Shixin Wang

The symplectic graph Sp(2d, q) is the collinearity graph of the symplectic space of dimension 2d over a finite field of order q. A k-regular graph on v vertices is a divisible design graph with parameters (v, k, lambda_1, lambda_2 ,m,n) if…

Combinatorics · Mathematics 2022-07-01 Vladislav V. Kabanov

The reconfiguration graph $R_k(G)$ of the $k$-colourings of a graph $G$ contains as its vertex set the $k$-colourings of $G$ and two colourings are joined by an edge if they differ in colour on just one vertex of $G$. We show that for each…

Combinatorics · Mathematics 2019-06-04 Carl Feghali , Jiří Fiala

A quasi-strongly regular graph of grade $p$ with parameters $(n, k, a; c_1, \ldots, c_p)$ is a $k$-regular graph of order $n$ such that any two adjacent vertices share $a$ common neighbours and any two non-adjacent vertices share $c_{i}$…

Combinatorics · Mathematics 2021-05-26 Songpon Sriwongsa , Pawaton Kaemawichanurat

The circumference $c(G)$ of a graph $G$ is the length of a longest cycle. By exploiting our recent results on resistance of snarks, we construct infinite classes of cyclically $4$-, $5$- and $6$-edge-connected cubic graphs with…

Discrete Mathematics · Computer Science 2013-11-12 Edita Máčajová , Ján Mazák

For any positive integer $k$, let $\mathcal{G}_k$ denote the set of finite groups $G$ such that all Cayley graphs ${\rm Cay}(G,S)$ are integral whenever $|S|\le k$. Est${\rm \acute{e}}$lyi and Kov${\rm \acute{a}}$cs \cite{EK14} classified…

Group Theory · Mathematics 2015-06-18 Xuanlong Ma , Kaishun Wang

Many conjectures and open problems in graph theory can either be reduced to cubic graphs or are directly stated for cubic graphs. Furthermore, it is known that for a lot of problems, a counterexample must be a snark, i.e. a bridgeless cubic…

Combinatorics · Mathematics 2023-09-27 Edita Máčajová , Giuseppe Mazzuoccolo , Vahan Mkrtchyan , Jean Paul Zerafa

We introduce and study a generalization of conformal rigidity for graphs. A graph is $k$-conformally rigid if the uniform edge weights simultaneously maximize the sum of the $k$ smallest nontrivial Laplacian eigenvalues and minimize the sum…

Combinatorics · Mathematics 2026-05-12 Henrique Assumpção , Gabriel Coutinho , Chris Godsil