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We show that for $ \eta>0 $ and sufficiently large $ n $, every 5-graph on $ n $ vertices with $\delta_{2}(H)\ge (91/216+\eta)\binom{n}{3}$ contains a Hamilton 2-cycle. This minimum 2-degree condition is asymptotically best possible.…

Combinatorics · Mathematics 2025-03-11 Jie Han , Lin Sun , Guanghui Wang

In this paper we prove a sufficient condition for the existence of a Hamilton cycle, which is applicable to a wide variety of graphs, including relatively sparse graphs. In contrast to previous criteria, ours is based on only two…

Combinatorics · Mathematics 2007-05-23 Dan Hefetz , Michael Krivelevich , Tibor Szabo

A classic theorem of Dirac from 1952 states that every graph with minimum degree at least n/2 contains a Hamiltonian cycle. In 1963, P\'osa conjectured that every graph with minimum degree at least 2n/3 contains the square of a Hamiltonian…

Combinatorics · Mathematics 2015-01-08 Louis DeBiasio , Safi Faizullah , Imdadullah Khan

We study the number of edge-disjoint Hamilton cycles one can guarantee in a sufficiently large graph G on n vertices with minimum degree d = (1/2+a)n. For any constant a > 0, we give an optimal answer in the following sense: let…

Combinatorics · Mathematics 2012-11-15 Daniela Kühn , John Lapinskas , Deryk Osthus

We investigate the appearance of the square of a Hamilton cycle in the model of randomly perturbed graphs, which is, for a given $\alpha \in (0,1)$, the union of any $n$-vertex graph with minimum degree $\alpha n$ and the binomial random…

Combinatorics · Mathematics 2025-07-18 Julia Böttcher , Olaf Parczyk , Amedeo Sgueglia , Jozef Skokan

In this paper, we consider a random geometric graph (RGG)~\(G\) on~\(n\) nodes with adjacency distance~\(r_n\) just below the Hamiltonicity threshold and construct Hamiltonian cycles using additional edges called bridges. The bridges by…

Probability · Mathematics 2021-12-13 Ghurumuruhan Ganesan

Given a graph $\Gamma = (V, E)$ on $n$ vertices and $m$ edges, we define the Erd\H{o}s-R\'{e}nyi graph process with host $\Gamma$ as follows. A permutation $e_1,\dots,e_m$ of $E$ is chosen uniformly at random, and for $t\leq m$ we let…

Combinatorics · Mathematics 2018-11-09 Tony Johansson

A graph is Hamiltonian if it contains a cycle passing through every vertex exactly once. A celebrated theorem of Dirac from 1952 asserts that every graph on $n\ge 3$ vertices with minimum degree at least $n/2$ is Hamiltonian. We refer to…

Combinatorics · Mathematics 2014-10-07 Michael Krivelevich , Choongbum Lee , Benny Sudakov

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

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

The paper is concerned with directed versions of Posa's theorem and Chvatal's theorem on Hamilton cycles in graphs. We show that for each a>0, every digraph G of sufficiently large order n whose outdegree and indegree sequences d_1^+ \leq…

Combinatorics · Mathematics 2010-02-23 Demetres Christofides , Peter Keevash , Daniela Kühn , Deryk Osthus

We show that for any fixed $\alpha>0$, cherry-quasirandom 3-graphs of positive density and sufficiently large order $n$ with minimum vertex degree $\alpha \binom n2$ have a tight Hamilton cycle. This solves a conjecture of Aigner-Horev and…

Combinatorics · Mathematics 2020-04-28 Luyining Gan , Jie Han

In this paper we consider the problem of finding ``as many edge-disjoint Hamilton cycles as possible'' in the binomial random digraph $D_{n,p}$. We show that a typical $D_{n,p}$ contains precisely the minimum between the minimum out- and…

Combinatorics · Mathematics 2025-02-04 Asaf Ferber , Adva Mond

There is a sizable literature on investigating the minimum and maximum numbers of cycles in a class of graphs. However, the answer is known only for special classes. This paper presents a result on the smallest number of cycles in…

Discrete Mathematics · Computer Science 2016-03-08 Bader F. AlBdaiwi

Given graphs $G_1,\ldots,G_s$ all on a common vertex set and a graph $H$ with $e(H) = s$, a copy of $H$ is \emph{transversal} or \emph{rainbow} if it contains one edge from each $G_i$. We establish a stability result for transversal…

Combinatorics · Mathematics 2024-03-18 Yangyang Cheng , Katherine Staden

In 1952, Dirac proved the following theorem about long cycles in graphs with large minimum vertex degrees: Every $n$-vertex $2$-connected graph $G$ with minimum vertex degree $\delta\geq 2$ contains a cycle with at least $\min\{2\delta,n\}$…

Data Structures and Algorithms · Computer Science 2024-04-15 Fedor V. Fomin , Petr A. Golovach , Danil Sagunov , Kirill Simonov

The semi-random graph process is an adaptive random graph process in which an online algorithm is initially presented an empty graph on $n$ vertices. In each round, a vertex $u$ is presented to the algorithm independently and uniformly at…

Combinatorics · Mathematics 2024-12-24 Alan Frieze , Pu Gao , Calum MacRury , Paweł Prałat , Gregory Sorkin

We provide a new lower bound on the length of the longest cycle of the binomial random graph $G(n,(1+\epsilon)/n)$ that holds w.h.p. for all $\epsilon=\epsilon(n)$ such that $\epsilon^3n\to \infty$. In the case $\epsilon\leq \epsilon_0$ for…

Combinatorics · Mathematics 2022-08-16 Michael Anastos

We prove that if G is an (n,d,lambda)-graph (a d-regular graph on n vertices, all of whose non-trivial eigenvalues are at most lambda) and the following conditions are satisfied: 1. d/lambda >= (log n)^{1+epsilon} for some constant…

Combinatorics · Mathematics 2012-01-10 Michael Krivelevich

We prove a new sufficient pair degree condition for tight Hamiltonian cycles in $3$-uniform hypergraphs that (asymptotically) improves the best known pair degree condition due to R\"odl, Ruci\'nski, and Szemer\'edi. For graphs, Chv\'atal…

Combinatorics · Mathematics 2021-02-04 Bjarne Schülke
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