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In this paper we study conditions which guarantee the existence of perfect matchings and perfect fractional matchings in uniform hypergraphs. We reduce this problem to an old conjecture by Erd\H{o}s on estimating the maximum number of edges…

Combinatorics · Mathematics 2012-02-01 Noga Alon , Peter Frankl , Hao Huang , Vojtech Rodl , Andrzej Rucinski , Benny Sudakov

The aim of this paper is to extend and generalise some work of Katona on the existence of perfect matchings or Hamilton cycles in graphs subject to certain constraints. The most general form of these constraints is that we are given a…

Combinatorics · Mathematics 2013-10-23 J. Robert Johnson

In his seminal 1976 paper, P\'osa showed that for all $p\geq C\log n/n$, the binomial random graph $G(n,p)$ is with high probability Hamiltonian. This leads to the following natural questions, which have been extensively studied: How well…

Combinatorics · Mathematics 2023-10-19 Nemanja Draganić , Stefan Glock , David Munhá Correia , Benny Sudakov

In this paper we investigate results of the form "every graph $G$ has a cycle $C$ such that the induced subgraph of $G$ on $V(G)\setminus V(C)$ has small maximum degree." Such results haven't been studied before, but are motivated by the…

Combinatorics · Mathematics 2016-07-26 Alexey Pokrovskiy

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

A graph is called Dirac if its minimum degree is at least half of the number of vertices in it. Joos and Kim showed that every collection $\mathbb{G}=\{G_1,\ldots,G_n\}$ of Dirac graphs on the same vertex set $V$ of size $n$ contains a…

Combinatorics · Mathematics 2026-04-14 Michael Anastos , Debsoumya Chakraborti

We prove a `resilience' version of Dirac's theorem in the setting of random regular graphs. More precisely, we show that, whenever $d$ is sufficiently large compared to $\varepsilon>0$, a.a.s. the following holds: let $G'$ be any subgraph…

Combinatorics · Mathematics 2020-06-25 Padraig Condon , Alberto Espuny Díaz , António Girão , Daniela Kühn , Deryk Osthus

Interaction between clique number $\omega(G) $ and chromatic number $\chi(G) $ of a graph is a well studied topic in graph theory. Perfect Graph Theorems are probably the most important results in this direction. Graph $G$ is called…

Logic in Computer Science · Computer Science 2018-12-31 Abhishek Kr Singh , Raja Natarajan

P\'osa's theorem states that any graph $G$ whose degree sequence $d_1 \le \ldots \le d_n$ satisfies $d_i \ge i+1$ for all $i < n/2$ has a Hamilton cycle. This degree condition is best possible. We show that a similar result holds for…

Combinatorics · Mathematics 2019-12-03 Padraig Condon , Alberto Espuny Díaz , Jaehoon Kim , Daniela Kühn , Deryk Osthus

We study two fundamental problems related to finding subgraphs: (1) given graphs G and H, Subgraph Test asks if H is isomorphic to a subgraph of G, (2) given graphs G, H, and an integer t, Packing asks if G contains t vertex-disjoint…

Data Structures and Algorithms · Computer Science 2014-10-06 Bart M. P. Jansen , Dániel Marx

Grohe and Marx proved that if G does not contain H as a topological minor, then there exist constants g=O(|V(H)|^4), D and t depending only on H such that G is a clique sum of graphs that either contain at most t vertices of degree greater…

Combinatorics · Mathematics 2012-09-04 Zdenek Dvorak

A graph is Hamiltonian if it contains a cycle passing through every vertex. One of the cornerstone results in the theory of random graphs asserts that for edge probability $p \gg \frac{\log n}{n}$, the random graph $G(n,p)$ is…

Combinatorics · Mathematics 2015-09-18 Michael Krivelevich , Choongbum Lee , Benny Sudakov

In this paper we show how to use simple partitioning lemmas in order to embed spanning graphs in a typical member of $G(n,p)$. Let the \emph{maximum density} of a graph $H$ be the maximum average degree of all the subgraphs of $H$. First,…

Combinatorics · Mathematics 2014-09-23 Asaf Ferber , Rajko Nenadov , Ueli Peter

The classic theorem of Gallai and Milgram (1960) generalizes several fundamental results in Graph Theory, such as Dilworth's theorem on posets and K\H{o}nig's theorem on matchings in bipartite graphs. The theorem asserts that for every…

Data Structures and Algorithms · Computer Science 2026-03-09 Fedor V. Fomin , Petr A. Golovach , Nikola Jedličková , Jan Kratochvíl , Danil Sagunov , Kirill Simonov

A graph is Hamiltonian if it contains a cycle which goes through all vertices exactly once. Determining if a graph is Hamiltonian is known as a NP-complete problem and no satisfactory characterization for these graphs has been found. In…

Combinatorics · Mathematics 2013-08-29 Thierry Vallee

We derive a sufficient condition for a sparse graph G on n vertices to contain a copy of a tree T of maximum degree at most d on (1-\epsilon)n vertices, in terms of the expansion properties of G. As a result we show that for fixed d\geq 2…

Combinatorics · Mathematics 2007-06-29 Noga Alon , Michael Krivelevich , Benny Sudakov

We say that a 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 $G$…

Combinatorics · Mathematics 2016-01-25 Andrew Treglown

Given a collection of hypergraphs $\textbf{H}=(H_1,\ldots,H_m)$ with the same vertex set, an $m$-edge graph $F\subset \cup_{i\in [m]}H_i$ is a transversal if there is a bijection $\phi:E(F)\to [m]$ such that $e\in E(H_{\phi(e)})$ for each…

Combinatorics · Mathematics 2023-06-26 Pranshu Gupta , Fabian Hamann , Alp Müyesser , Olaf Parczyk , Amedeo Sgueglia

For all integers $n \geq k > d \geq 1$, let $m_{d}(k,n)$ be the minimum integer $D \geq 0$ such that every $k$-uniform $n$-vertex hypergraph $\mathcal H$ with minimum $d$-degree $\delta_{d}(\mathcal H)$ at least $D$ has an optimal matching.…

Combinatorics · Mathematics 2024-04-17 Dong Yeap Kang , Tom Kelly , Daniela Kühn , Deryk Osthus , Vincent Pfenninger

We provide a degree condition on a regular $n$-vertex graph $G$ which ensures the existence of a near optimal packing of any family $\mathcal H$ of bounded degree $n$-vertex $k$-chromatic separable graphs into $G$. In general, this degree…

Combinatorics · Mathematics 2018-11-12 Padraig Condon , Jaehoon Kim , Daniela Kühn , Deryk Osthus
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