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Erd\H{o}s and Hajnal conjectured that for every graph $H$, there exists $c>0$ such that every $H$-free graph $G$ has a clique or a stable set of size at least $|G|^c$ (a graph is $H$-free if it has no induced subgraph isomorphic to $H$).…

Combinatorics · Mathematics 2026-04-21 Tung Nguyen , Alex Scott , Paul Seymour

For a subgraph $G$ of the blow-up of a graph $F$, we let $\delta^*(G)$ be the smallest minimum degree over all of the bipartite subgraphs of $G$ induced by pairs of parts that correspond to edges of $F$. In [Triangle-factors in a balanced…

Combinatorics · Mathematics 2021-03-18 Beka Ergemlidze , Theodore Molla

The toughness of a graph $G$ is defined as the minimum value of $|S|/c(G-S)$ over all cutsets $S$ of $G$ if $G$ is noncomplete, and is defined to be $\infty$ if $G$ is complete. For a real number $t$, we say that $G$ is $t$-tough if its…

Combinatorics · Mathematics 2025-07-02 Lili Hao , Hui Ma , Songling Shan , Weihua Yang

An old problem raised independently by Jacobson and Sch\"onheim asks to determine the maximum $s$ for which every graph with $m$ edges contains a pair of edge-disjoint isomorphic subgraphs with $s$ edges. In this paper we determine this…

Combinatorics · Mathematics 2012-10-16 Choongbum Lee , Po-Shen Loh , Benny Sudakov

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 set of vertices $W$ of a graph $G$ is a resolving set if every vertex of $G$ is uniquely determined by its vector of distances to $W$. In this paper, the Maker-Breaker resolving game is introduced. The game is played on a graph $G$ by…

Combinatorics · Mathematics 2020-05-28 Cong X. Kang , Sandi Klavžar , Ismael G. Yero , Eunjeong Yi

An $\textit{identifying code}$ of a closed-twin-free graph $G$ is a set $S$ of vertices of $G$ such that any two vertices in $G$ have a distinct intersection between their closed neighborhood and $S$. It was conjectured that there exists a…

Combinatorics · Mathematics 2024-07-24 Dipayan Chakraborty , Florent Foucaud , Michael A. Henning , Tuomo Lehtilä

We consider a biased version of Maker-Breaker domination games, which were recently introduced by Gledel, Ir{\v{s}}i{\v{c}}, and Klav{\v{z}}ar. Two players, Dominator and Staller, alternatingly claim vertices of a graph $G$ where Dominator…

Combinatorics · Mathematics 2024-08-02 Ali Deniz Bagdas , Dennis Clemens , Fabian Hamann , Yannick Mogge

Let $G$ be a graph with vertex set $V(G)$. Let $n$ and $k$ be non-negative integers such that $n + 2k \leq |V(G)| - 2$ and $|V(G)| - n$ is even. If when deleting any $n$ vertices of $G$ the remaining subgraph contains a matching of $k$…

Combinatorics · Mathematics 2007-05-23 Guizhen Liu , Qinglin Yu

We study the problem of embedding graphs in the plane as good geometric spanners. That is, for a graph $G$, the goal is to construct a straight-line drawing $\Gamma$ of $G$ in the plane such that, for any two vertices $u$ and $v$ of $G$,…

Data Structures and Algorithms · Computer Science 2020-02-14 Oswin Aichholzer , Manuel Borrazzo , Prosenjit Bose , Jean Cardinal , Fabrizio Frati , Pat Morin , Birgit Vogtenhuber

We say that a (di)graph $G$ has a perfect $H$-packing if there exists a set of vertex-disjoint copies of $H$ which cover all the vertices in $G$. The seminal Hajnal--Szemer\'edi theorem characterises the minimum degree that ensures a graph…

Combinatorics · Mathematics 2015-01-27 Andrew Treglown

We prove that any graph $G$ of minimum degree greater than $2k^2-1$ has a $(k+1)$-connected induced subgraph $H$ such that the number of vertices of $H$ that have neighbors outside of $H$ is at most $2k^2-1$. This generalizes a classical…

Combinatorics · Mathematics 2016-11-04 Irena Penev , Stéphan Thomassé , Nicolas Trotignon

We prove that there is a constant $c >0$, such that whenever $p \ge n^{-c}$, with probability tending to 1 when $n$ goes to infinity, every maximum triangle-free subgraph of the random graph $G_{n,p}$ is bipartite. This answers a question…

Probability · Mathematics 2009-08-27 Graham Brightwell , Konstantinos Panagiotou , Angelika Steger

Given hypergraphs H and F, an F-factor in H is a spanning subgraph consisting of vertex disjoint copies of F. Let K_4^3-e denote the 3-uniform hypergraph on 4 vertices with 3 edges. We show that for \gamma>0 there exists an integer n_0 such…

Combinatorics · Mathematics 2013-01-01 Allan Lo , Klas Markström

We consider a game in which a cop searches for a moving robber on a graph using distance probes, which is a slight variation on one introduced by Seager. Carragher, Choi, Delcourt, Erickson and West showed that for any n-vertex graph $G$…

Combinatorics · Mathematics 2020-08-12 John Haslegrave , Richard A. B. Johnson , Sebastian Koch

In this note we show the following strengthening of a multipartite version of the Hajnal--Szemer\'edi theorem. For an integer $r \ge 3$ and $\gamma > 0$, there exists a constant $C$ such that if $p\ge Cn^{-2/r}(\log n)^{1/{r \choose 2}}$…

Combinatorics · Mathematics 2023-11-03 Jie Han , Jie Hu , Donglei Yang

Results on the existence of various types of spanning subgraphs of graphs are milestones in structural graph theory and have been diversified in several directions. In the present paper, we consider "local" versions of such statements. In…

Combinatorics · Mathematics 2023-04-07 Thomas Böhme , Jochen Harant , Matthias Kriesell , Samuel Mohr , Jens M. Schmidt

In this paper we study the (a : b) Maker-Breaker Connectivity game, played on the edge-set of the complete graph on n vertices. We determine the winner for almost all values of a and b.

Combinatorics · Mathematics 2016-08-14 Dan Hefetz , Mirjana Rakić , Miloš Stojaković

We prove that there exists an absolute constant $C>0$ such that, for any positive integer $k$, every graph $G$ with minimum degree at least $Ck$ admits a vertex-partition $V(G)=S\cup T$, where both $G[S]$ and $G[T]$ have minimum degree at…

Combinatorics · Mathematics 2023-06-16 Jie Ma , Hehui Wu

A class of graphs is bridge-addable if given a graph $G$ in the class, any graph obtained by adding an edge between two connected components of $G$ is also in the class. We prove a conjecture of McDiarmid, Steger, and Welsh, that says that…

Combinatorics · Mathematics 2023-06-23 Guillaume Chapuy , Guillem Perarnau
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