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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

The celebrated dependent random choice lemma states that in a bipartite graph an average vertex (weighted by its degree) has the property that almost all small subsets $S$ in its neighborhood has common neighborhood almost as large as in…

Combinatorics · Mathematics 2022-01-27 Tao Jiang , Sean Longbrake

A graph is called $d$-rigid if there exists a generic embedding of its vertex set into $\mathbb{R}^d$ such that every continuous motion of the vertices that preserves the lengths of all edges actually preserves the distances between all…

Combinatorics · Mathematics 2023-12-13 Michael Krivelevich , Alan Lew , Peleg Michaeli

We study structural conditions in dense graphs that guarantee the existence of vertex-spanning substructures such as Hamilton cycles. It is easy to see that every Hamiltonian graph is connected, has a perfect fractional matching and,…

Combinatorics · Mathematics 2023-06-21 Richard Lang , Nicolás Sanhueza-Matamala

A graph G on n vertices is Hamiltonian if it contains a cycle of length n and pancyclic if it contains cycles of length $\ell$ for all $3 \le \ell \le n$. Write $\alpha(G)$ for the independence number of $G$, i.e. the size of the largest…

Combinatorics · Mathematics 2009-03-27 Peter Keevash , Benny Sudakov

Motivated by Thomassen's well-known line graph conjecture, many researchers have explored sufficient conditions for claw-free graphs to be Hamiltonian or Hamilton-connected. In 1994, Ageev proved that every $2$-connected claw-free graph…

Combinatorics · Mathematics 2026-03-05 Kenta Ozeki , Leilei Zhang

Given a graph $G$ whose edges are perfectly reliable and whose nodes each operate independently with probability $p\in[0,1],$ the node reliability of $G$ is the probability that at least one node is operational and that the operational…

Combinatorics · Mathematics 2018-02-14 Jason Brown , Lucas Mol

We prove that every $3$-graph $H$ on $n$ vertices with minimum codegree $\delta_2(H) \geq 7n/9 + o(n)$ contains the square of a tight Hamilton cycle. This strengthens a theorem of Bedenknecht and Reiher that $\delta_2(H) \geq 4n/5 + o(n)$…

Combinatorics · Mathematics 2026-03-31 Debmalya Bandyopadhyay , Allan Lo , Richard Mycroft

In a sequence of four papers, we prove the following results (via a unified approach) for all sufficiently large $n$: (i) [1-factorization conjecture] Suppose that $n$ is even and $D\geq 2\lceil n/4\rceil -1$. Then every $D$-regular graph…

Combinatorics · Mathematics 2014-10-24 Béla Csaba , Daniela Kühn , Allan Lo , Deryk Osthus , Andrew Treglown

Let $D$ be a strong digraph on $n\geq 4$ vertices. In [2, J. Graph Theory 22 (2) (1996) 181-187)], J. Bang-Jensen, G. Gutin and H. Li proved the following theorems: If (*) $d(x)+d(y)\geq 2n-1$ and $min \{d(x), d(y)\}\geq n-1$ for every pair…

Combinatorics · Mathematics 2012-09-21 S. Kh. Darbinyan , I. A. Karapetyan

Robustness is a critical measure of the resilience of large networked systems, such as transportation and communication networks. Most prior works focus on the global robustness of a given graph at large, e.g., by measuring its overall…

Social and Information Networks · Computer Science 2015-01-09 Hau Chan , Shuchu Han , Leman Akoglu

Directed acyclic graphs (DAGs) can be characterised as directed graphs whose strongly connected components are isolated vertices. Using this restriction on the strong components, we discover that when $m = cn$, where $m$ is the number of…

Combinatorics · Mathematics 2020-04-21 Élie de Panafieu , Sergey Dovgal

We investigate the existence of a rainbow Hamilton cycle in a uniformly edge-coloured randomly perturbed digraph. We show that for every $\delta \in (0,1)$ there exists $C = C(\delta) > 0$ such that the following holds. Let $D_0$ be an…

Combinatorics · Mathematics 2024-11-20 Kyriakos Katsamaktsis , Shoham Letzter , Amedeo Sgueglia

Goodman proved that the sum of the number of triangles in a graph on $n$ nodes and its complement is at least $n^3/24$; in other words, this sum is minimized, asymptotically, by a random graph with edge density $1/2$. Erd\H{o}s conjectured…

Combinatorics · Mathematics 2019-12-09 Endre Csóka , Tamás Hubai , László Lovász

Let $G$ be a graph on $n\geq 3$ vertices. A graph $G$ is almost distance-hereditary if each connected induced subgraph $H$ of $G$ has the property $d_{H}(x,y)\leq d_{G}(x,y)+1$ for any pair of vertices $x,y\in V(H)$. A graph $G$ is called…

Combinatorics · Mathematics 2016-06-13 Bing Chen , Bo Ning

In this paper, we study the trajectory of a classic SIR epidemic on a family of dynamic random graphs of fixed size, whose set of edges continuously evolves over time. We set general infection and recovery times, and start the epidemic from…

Probability · Mathematics 2025-01-17 Marta Milewska , Remco van der Hofstad , Bert Zwart

We show how to adjust a very nice coupling argument due to McDiarmid in order to prove/reprove in a novel way results concerning Hamilton cycles in various models of random graph and hypergraphs. In particular, we firstly show that for…

Combinatorics · Mathematics 2015-02-09 Asaf Ferber

Given a graph $G$ whose edges are perfectly reliable and whose nodes each operate independently with probability $p\in[0,1],$ the node reliability of $G$ is the probability that at least one node is operational and that the operational…

Combinatorics · Mathematics 2017-07-17 Jason Brown , Lucas Mol

More than 40 years ago Chv\'atal introduced a new graph invariant, which he called graph toughness. From then on a lot of research has been conducted, mainly related to the relationship between toughness conditions and the existence of…

Combinatorics · Mathematics 2024-06-26 Vladimir I. Benediktovich

We present eighteen exact analogs of six well-known fundamental Theorems (due to Dirac, Nash-Williams and Jung) in hamiltonian graph theory providing alternative compositions of graph invariants. In Theorems 1-3 we give three lower bounds…

Combinatorics · Mathematics 2012-04-10 Zh. G. Nikoghosyan