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For any even integer $k\ge 6$, integer $d$ such that $k/2\le d\le k-1$, and sufficiently large $n\in (k/2)\mathbb N$, we find a tight minimum $d$-degree condition that guarantees the existence of a Hamilton $(k/2)$-cycle in every…

Combinatorics · Mathematics 2021-02-22 Hiep Han , Jie Han , Yi Zhao

The notion of treewidth, introduced by Robertson and Seymour in their seminal Graph Minors series, turned out to have tremendous impact on graph algorithmics. Many hard computational problems on graphs turn out to be efficiently solvable in…

Data Structures and Algorithms · Computer Science 2019-09-24 Michał Ziobro , Marcin Pilipczuk

In 2006, K\"{u}hn and Osthus showed that if a 3-graph H on n vertices has minimum co-degree at least (1/4 +o(1))n and n is even then H has a loose Hamilton cycle. In this paper, we prove that the minimum co-degree of n/4 suffices. The…

Combinatorics · Mathematics 2013-08-06 Andrzej Czygrinow , Theodore Molla

A $3$-uniform loose cycle, denoted by $C_t$, is a $3$-graph on $t$ vertices whose vertices can be arranged cyclically so that each hyperedge consists of three consecutive vertices, and any two consecutive hyperedges share exactly one…

Combinatorics · Mathematics 2025-05-20 Yangyang Cheng , Mengjiao Rao , Guanghui Wang , Yuqi Zhao

We investigate the emergence of spanning structures in sparse pseudo-random $k$-uniform hypergraphs, using the following comparatively weak notion of pseudo-randomness. A $k$-uniform hypergraph $H$ on $n$ vertices is called…

Combinatorics · Mathematics 2021-08-11 Hiep Hàn , Jie Han , Patrick Morris

We show that every sufficiently large oriented graph $G$ with minimum indegree and outdegree both at least $(3|V(G)|-1)/8$ contains every orientation of a Hamilton cycle. This result improves the approximate bound established by Kelly and…

Combinatorics · Mathematics 2026-01-01 Guanghui Wang , Yun Wang , Zhiwei Zhang

We present a method which provides a unified framework for most stability theorems that have been proved in graph and hypergraph theory. Our main result reduces stability for a large class of hypergraph problems to the simpler question of…

Combinatorics · Mathematics 2022-11-15 Xizhi Liu , Dhruv Mubayi , Christian Reiher

We survey some recent results on long-standing conjectures regarding Hamilton cycles in directed graphs, oriented graphs and tournaments. We also combine some of these to prove the following approximate result towards Kelly's conjecture on…

Combinatorics · Mathematics 2010-06-04 Daniela Kühn , Deryk Osthus

In a seminal work, K\"uhn, Osthus, Townsend, and Zhao used the hypergraph container method to determine the typical structure of oriented graphs and digraphs avoiding a fixed tournament or cycle. Their main tool, a container theorem for…

Combinatorics · Mathematics 2026-05-20 Meili Liang , Yue Guan , Ruiling Zheng , Jianxi Liu

We revisit results obtained in [F. Harary, U. Peled, Hamiltonian threshold graphs, Discrete Appl.~Math., 16 (1987), 11--15], where several necessary and necessary and sufficient conditions for a connected threshold graph to be Hamiltonian…

Combinatorics · Mathematics 2021-02-17 Milica Andelic , Tamara Koledin , Zoran Stanic

We present a necessary and sufficient condition for existence of a contractible Hamiltonian Cycle in the edge graph of equivelar maps on surfaces. We also present an algorithm to construct such cycles. This is further generalized and shown…

Combinatorics · Mathematics 2012-02-21 Dipendu Maity , Ashish Kumar Upadhyay

This paper presents sufficient conditions for Hamiltonian paths and cycles in graphs. Letting $\lambda\left( G\right) $ denote the spectral radius of the adjacency matrix of a graph $G,$ the main results of the paper are: (1) Let $k\geq1,$…

Combinatorics · Mathematics 2016-11-08 Vladimir Nikiforov

Finding general conditions which ensure that a graph is Hamiltonian is a central topic in graph theory. An old and well known conjecture in the area states that any $d$-regular $n$-vertex graph $G$ whose second largest eigenvalue in…

Combinatorics · Mathematics 2023-03-10 Stefan Glock , David Munhá Correia , Benny Sudakov

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

It follows from the Marcus-Spielman-Srivastava proof of the Kadison-Singer conjecture that if $G=(V,E)$ is a $\Delta$-regular dense expander then there is an edge-induced subgraph $H=(V,E_H)$ of $G$ of constant maximum degree which is also…

Distributed, Parallel, and Cluster Computing · Computer Science 2021-03-09 Luca Becchetti , Andrea Clementi , Emanuele Natale , Francesco Pasquale , Luca Trevisan

Rigidity, arising in discrete geometry, is the property of a structure that does not flex. Laman provides a combinatorial characterization of rigid graphs in the Euclidean plane, and thus rigid graphs in the Euclidean plane have…

Combinatorics · Mathematics 2018-06-14 Xiaofeng Gu

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

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

A set of vertices in a graph is a Hamiltonian subset if it induces a subgraph containing a Hamiltonian cycle. Kim, Liu, Sharifzadeh and Staden proved that among all graphs with minimum degree $d$, $K_{d+1}$ minimises the number of…

Combinatorics · Mathematics 2023-01-19 Stijn Cambie , Jun Gao , Hong Liu

Rigidity is the property of a structure that does not flex. It is well studied in discrete geometry and mechanics, and has applications in material science, engineering and biological sciences. A bar-and-joint framework is a pair $(G,p)$ of…

Combinatorics · Mathematics 2021-03-02 Sebastian M. Cioabă , Sean Dewar , Xiaofeng Gu