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We prove that the clique graph operator $k$ is divergent on a locally cyclic graph $G$ (i.e. $N_G(v)$ is a circle) with minimum degree $\delta(G)=6$ if and only if $G$ is $6$-regular. The clique graph $kG$ of a graph $G$ has the maximal…

Combinatorics · Mathematics 2021-03-30 Markus Baumeister , Anna M. Limbach

In this paper, we are concerned with sufficient conditions for the existence of a $\{P_{2},P_{2k+1}\}$-factor. We prove that for $k\geq 3$, there exists $\varepsilon_{k}>0$ such that if a graph $G$ satisfies $\sum_{0\leq j\leq…

Combinatorics · Mathematics 2017-05-25 Yoshimi Egawa , Michitaka Furuya , Kenta Ozeki

Given a family $\mathcal{F}$ of bipartite graphs, the {\it Zarankiewicz number} $z(m,n,\mathcal{F})$ is the maximum number of edges in an $m$ by $n$ bipartite graph $G$ that does not contain any member of $\mathcal{F}$ as a subgraph (such…

Combinatorics · Mathematics 2023-01-11 Tao Jiang , Sean Longbrake , Jie Ma

A graph is said to be $\mathcal{H}(n, \Delta)$-universal if it contains every graph on $n$ vertices with maximum degree at most $\Delta$. Using a `matching-based' embedding technique introduced by Alon and F\"uredi, Dellamonica, Kohayakawa,…

Combinatorics · Mathematics 2017-07-26 Asaf Ferber , Rajko Nenadov

In 2022, Holmsen showed that any graph with at least \( c \binom{n}{r} \) \(r\)-cliques but no induced complete $r$-partite graph $K_{2,\ldots, 2}$ must contain a clique of order \(\Omega(c^{2^{r-1}} n)\). In this paper, we study graphs…

Combinatorics · Mathematics 2025-11-18 Nannan Chen , Yulai Ma , Fan Yang

Let ccl(G) denote the order of the largest complete minor in a graph G (also called the contraction clique number) and let G(n,p) denote a random graph on n vertices with edge probability p. Bollobas, Catlin and Erdos asymptotically…

Combinatorics · Mathematics 2007-05-23 N. Fountoulakis , D. Kühn , D. Osthus

A graph $G$ on $n$ vertices is \textit{pancyclic} if it contains cycles of length $t$ for all $3 \leq t \leq n$. In this paper we prove that for any fixed $\epsilon>0$, the random graph $G(n,p)$ with $p(n)\gg n^{-1/2}$ asymptotically almost…

Combinatorics · Mathematics 2009-06-09 Michael Krivelevich , Choongbum Lee , Benny Sudakov

Emergence of dominating cliques in Erd\"os-R\'enyi random graph model ${\bbbg(n,p)}$ is investigated in this paper. It is shown this phenomenon possesses a phase transition. Namely, we have argued that, given a constant probability $p$, an…

Combinatorics · Mathematics 2008-05-15 Martin Nehez , Daniel Olejar , Michal Demetrian

Recently there has been much interest in studying random graph analogues of well known classical results in extremal graph theory. Here we follow this trend and investigate the structure of triangle-free subgraphs of $G(n,p)$ with high…

Combinatorics · Mathematics 2015-07-21 Peter Allen , Julia Böttcher , Yoshiharu Kohayakawa , Barnaby Roberts

A graph $G$ with four or more vertices is called bicritical if the removal of any pair of distinct vertices of $G$ results in a graph with a perfect matching. A bicritical graph is minimal if the deletion of each edge results in a…

Combinatorics · Mathematics 2024-10-15 Jing Guo , Hailun Wu , Heping Zhang

Sidorenko's conjecture states that the number of copies of any given bipartite graph in another graph of given density is asymptotically minimized by a random graph. The forcing conjecture further strengthens this, claiming that any…

Combinatorics · Mathematics 2024-12-18 Aldo Kiem , Olaf Parczyk , Christoph Spiegel

Let $F$ be a graph on $r$ vertices and let $G$ be a graph on $n$ vertices. Then an $F$-factor in $G$ is a subgraph of $G$ composed of $n/r$ vertex-disjoint copies of $F$, if $r$ divides $n$. In other words, an $F$-factor yields a partition…

Combinatorics · Mathematics 2025-08-13 Fabian Burghart , Annika Heckel , Marc Kaufmann , Noela Müller , Matija Pasch

A $1$-factorization of a graph $G$ is a collection of edge-disjoint perfect matchings whose union is $E(G)$. A trivial necessary condition for $G$ to admit a $1$-factorization is that $|V(G)|$ is even and $G$ is regular; the converse is…

Combinatorics · Mathematics 2018-04-09 Asaf Ferber , Vishesh Jain

A theorem of R\"odl states that for every fixed $F$ and $\varepsilon>0$ there is $\delta=\delta_F(\varepsilon)$ so that every induced $F$-free graph contains a vertex set of size $\delta n$ whose edge density is either at most $\varepsilon$…

Combinatorics · Mathematics 2023-08-02 Lior Gishboliner , Asaf Shapira

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

A graph $G$ contains $H$ as an \emph{immersion} if there is an injective mapping $\phi: V(H)\rightarrow V(G)$ such that for each edge $uv\in E(H)$, there is a path $P_{uv}$ in $G$ joining vertices $\phi(u)$ and $\phi(v)$, and all the paths…

Combinatorics · Mathematics 2022-08-02 Hong Liu , Guanghui Wang , Donglei Yang

A pseudo [2,b]-factor of a graph G is a spanning subgraph in which each component C on at least three vertices is a [2,b]-graph. The main contibution of this paper, is to give an upper bound to the number of components that are edges or…

Discrete Mathematics · Computer Science 2012-04-18 Siham Bekkai

An odd $[1,b]$-factor of a graph $G$ is a spanning subgraph $H$ such that for each vertex $v \in V(G)$, $d_H(v)$ is odd and $1\le d_H(v) \le b$. Let $\lambda_3(G)$ be the third largest eigenvalue of the adjacency matrix of $G$. For positive…

Combinatorics · Mathematics 2020-03-31 Sungeun Kim , Suil O , Jihwan Park , Hyo Ree

For any graph (hypergraph) $G$ with vertex set $V$ and edge set $E$, we define its incidence bipartite graph $\mathcal{I}(G)$ as the bipartite graph with bipartition $(E, V)$, where an edge $e \in E$ is adjacent to a vertex $v \in V$ in…

Combinatorics · Mathematics 2026-01-05 Yuping Gao , Songling Shan , Gexin Yu

The biclique partition number of a graph $G= (V,E)$, denoted $bp(G)$, is the minimum number of pairwise edge disjoint complete bipartite subgraphs of $G$ so that each edge of $G$ belongs to exactly one of them. It is easy to see that $…

Combinatorics · Mathematics 2024-01-10 Tom Bohman , Jakob Hofstad
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