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We study the complexity of the Graph Isomorphism problem on graph classes that are characterized by a finite number of forbidden induced subgraphs, focusing mostly on the case of two forbidden subgraphs. We show hardness results and develop…

Data Structures and Algorithms · Computer Science 2015-03-20 Stefan Kratsch , Pascal Schweitzer

We call a graph $G$ pancyclic if it contains at least one cycle of every possible length $m$, for $3\le m\le |V(G)|$. In this paper, we define a new property called chorded pancyclicity. We explore forbidden subgraphs in claw-free graphs…

Combinatorics · Mathematics 2017-09-21 Megan Cream , Ronald J. Gould , Victor Larsen

Here in particular, we give a characterization of Quasi-line Graphs in terms of forbidden induced subgraphs. In general, we prove a necessary and sufficient condition for a graph to be a union of two cliques.

Combinatorics · Mathematics 2015-10-26 Medha Dhurandhar

Let $Y$ be the subdivided claw, the $7$-vertex tree obtained from a claw $K_{1,3}$ by subdividing each edge exactly once. We characterize the graphs (finite and infinite) that do not have $Y$ as a subgraph, or, equivalently, do not have $Y$…

Combinatorics · Mathematics 2026-02-05 Sarah Allred , M. N. Ellingham

This paper deals with graph classes characterization and recognition. A popular way to characterize a graph class is to list a minimal set of forbidden induced subgraphs. Unfortunately this strategy usually does not lead to an efficient…

Data Structures and Algorithms · Computer Science 2020-07-21 Laurent Feuilloley , Michel Habib

We describe ${\rm Forb}\{K_{1,3}, \bar {K_{1,3}}\}$, the class of graphs $G$ such that $G$ and its complement $\bar{G}$ are claw-free. With few exceptions, it is made of graphs whose connected components consist of cycles of length at least…

Combinatorics · Mathematics 2020-12-01 Maurice Pouzet , Hamza Si Kaddour , Nicolas Trotignon

We describe $Forb\{K_{1,3}, \overline {K_{1,3}}\}$, the class of graphs $G$ such that $G$ and its complement $ \overline{G}$ are claw-free. With few exceptions, it is made of graphs whose connected components consist of cycles of length at…

Combinatorics · Mathematics 2008-12-09 Maurice Pouzet , Hamza Si Kaddour

For every graph $X$, we consider the class of all connected $\{K_{1,3}, X\}$-free graphs which are distinct from an odd cycle and have independence number at least $4$, and we show that all graphs in the class are perfect if and only if $X$…

We say that a graph $G$ on $n$ vertices is $\{H,F\}$-$o$-heavy if every induced subgraph of $G$ isomorphic to $H$ or $F$ contains two nonadjacent vertices with degree sum at least $n$. Generalizing earlier sufficient forbidden subgraph…

Combinatorics · Mathematics 2024-09-23 Wangyi Shang , Hajo Broersma , Shenggui Zhang , Binlong Li

We introduce the factorization graph of a finite group and study its connectedness and forbidden structures. We characterize all finite groups with connected factorization graphs and classify those with connected bipartite factorization…

Group Theory · Mathematics 2019-12-02 Mohammad Farrokhi Derakhshandeh Ghouchan , Ali Azimi

A graph is circle if its vertices are in correspondence with a family of chords in a circle in such a way that every two distinct vertices are adjacent if and only if the corresponding chords have nonempty intersection. Even though there…

Discrete Mathematics · Computer Science 2023-04-04 Flavia Bonomo-Braberman , Guillermo A. Durán , Nina Pardal , Martín D. Safe

Let $G$ be a graph on $n\geq 3$ vertices, claw the bipartite graph $K_{1,3}$, and $Z_i$ the graph obtained from a triangle by attaching a path of length $i$ to its one vertex. $G$ is called 1-heavy if at least one end vertex of each induced…

Combinatorics · Mathematics 2013-01-07 Bo Ning , Bing Chen , Shenggui Zhang

We initiate the study of graph classes of power-bounded clique-width, that is, graph classes for which there exist integers $k$ and $\ell$ such that the $k$-th powers of the graphs are of clique-width at most $\ell$. We give sufficient and…

Combinatorics · Mathematics 2023-04-04 Flavia Bonomo , Luciano N. Grippo , Martin Milanič , Martín D. Safe

In 1981, Duffus, Gould, and Jacobson showed that every connected graph either has a Hamiltonian path, or contains a claw ($K_{1,3}$) or a net (a fixed six-vertex graph) as an induced subgraph. This implies that subject to being connected,…

Combinatorics · Mathematics 2022-08-09 Joseph Cheriyan , Sepehr Hajebi , Zishen Qu , Sophie Spirkl

In this paper, we study different forbidden subgraph characterizations of the prime-order element graph $\Gamma(G)$ defined on a finite group $G$. Its set of vertices is the group $G$ and two vertices $x,y \in G$ are adjacent if the order…

Combinatorics · Mathematics 2024-12-31 Tapa Manna , Angsuman Das , Baby Bhattacharya

We continue the study of the recently-introduced C123-framework, for (simple) graph problems restricted to inputs specified by the forbidding of some finite set of subgraphs, to more general graph problems possibly involving multiedges and…

Combinatorics · Mathematics 2026-02-12 Tala Eagling-Vose , Barnaby Martin , Daniel Paulusma , Siani Smith

We collect some general results on graph limits associated to hereditary classes of graphs. As examples, we consider some classes defined by forbidden subgraphs and some classes of intersection graphs, including triangle-free graphs,…

Combinatorics · Mathematics 2013-03-29 Svante Janson

We introduce a characterization for split graphs by using edge contraction. Then, we use it to prove that any ($2K_{2}$, claw)-free graph with $\alpha(G) \geq 3$ is a split graph. Also, we apply it to characterize any pseudo-split graph.…

Combinatorics · Mathematics 2022-05-05 Hany Ibrahim

Chordal graphs and chordal bigraphs enjoy beautiful characterizations, in terms of forbidden subgraphs, vertex/edge orderings, vertex/edge separating sets, and tree-like representations. In this paper, we introduce chordal signed graphs and…

Combinatorics · Mathematics 2026-01-09 Jing Huang , Ying Ying Ye

The claw number of a graph $G$ is the largest number $v$ such that $K_{1,v}$ is an induced subgraph of $G$. Interval graphs with claw number at most $v$ are cluster graphs when $v = 1$, and are proper interval graphs when $v = 2$. Let…

Combinatorics · Mathematics 2021-09-24 Rain Jiang , Kai Jiang , Minghui Jiang
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