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The Erd\H{o}s-Hajnal conjecture says that, for every graph $H$, there exists $c>0$ such that every $H$-free graph on $n$ vertices has a clique or stable set of size at least $n^c$. In this paper we are concerned with the case when $H$ is a…

Combinatorics · Mathematics 2024-10-22 Tung Nguyen , Alex Scott , Paul Seymour

For two fixed graphs $T$ and $H$ let $ex(G(n,p),T,H)$ be the random variable counting the maximum number of copies of $T$ in an $H$-free subgraph of the random graph $G(n,p)$. We show that for the case $T=K_m$ and $\chi(H)> m$ the behavior…

Combinatorics · Mathematics 2017-11-21 Noga Alon , Alexandr Kostochka , Clara Shikhelman

In this paper, we are interested in the mixing behaviour of simple random walks on inhomogeneous directed graphs. We focus our study on the Chung-Lu digraph, which is an inhomogeneous network that generalizes the Erd\H{o}s-R\'enyi digraph.…

Probability · Mathematics 2024-09-25 Alessandra Bianchi , Giacomo Passuello

We study the asymptotics for sparse exponential random graph models where the parameters may depend on the number of vertices of the graph. We obtain exact estimates for the mean and variance of the limiting probability distribution and the…

Probability · Mathematics 2017-04-19 Mei Yin , Lingjiong Zhu

We introduce a very general model of an inhomogenous random graph with independence between the edges, which scales so that the number of edges is linear in the number of vertices. This scaling corresponds to the p=c/n scaling for G(n,p)…

Probability · Mathematics 2011-11-10 Bela Bollobas , Svante Janson , Oliver Riordan

We explore the Wilks phenomena in two random graph models: the $\beta$-model and the Bradley-Terry model. For two increasing dimensional null hypotheses, including a specified null $H_0: \beta_i=\beta_i^0$ for $i=1,\ldots, r$ and a…

Statistics Theory · Mathematics 2025-06-27 Ting Yan , Yuanzhang Li , Jinfeng Xu , Yaning Yang , Ji Zhu

It is shown that the number of labelled graphs with n vertices that can be embedded in the orientable surface S_g of genus g grows asymptotically like $c^{(g)}n^{5(g-1)/2-1}\gamma^n n!$ where $c^{(g)}>0$, and $\gamma \approx 27.23$ is the…

Combinatorics · Mathematics 2012-03-15 Guillaume Chapuy , Eric Fusy , Omer Gimenez , Bojan Mohar , Marc Noy

We propose and study a hierarchical algorithm to generate graphs having a predetermined distribution of cliques, the fully connected subgraphs. The construction mechanism may be either random or incorporate preferential attachment. We…

Physics and Society · Physics 2009-11-13 Gregor Kaczor , Claudius Gros

The well-known Erd\H{o}s-Hajnal conjecture states that for any graph $F$, there exists $\epsilon>0$ such that every $n$-vertex graph $G$ that contains no induced copy of $F$ has a homogeneous set of size at least $n^{\epsilon}$. We consider…

Combinatorics · Mathematics 2023-05-03 Maria Axenovich , Domagoj Bradač , Lior Gishboliner , Dhruv Mubayi , Lea Weber

Bollob\'{a}s and Nikiforov (J. Combin. Theory Ser. B. 97 (2007) 859-865) conjectured that for a graph $G$ with $e(G)$ edges and the clique number $\omega(G)$, then $ \lambda_{1}^{2}+\lambda_{2}^{2}\leq…

Combinatorics · Mathematics 2025-01-14 Chunmeng Liu , Changjiang Bu

We study asymptotics of perfect matchings on a large class of graphs called the contracting square-hexagon lattice, which is constructed row by row from either a row of a square grid or a row of a hexagonal lattice. We assign the graph…

Probability · Mathematics 2020-09-01 Cédric Boutillier , Zhongyang Li

We give a common description of Simon, Barab\'asi--Albert, II-PA and Price growth models, by introducing suitable random graph processes with preferential attachment mechanisms. Through the II-PA model, we prove the conditions for which the…

Probability · Mathematics 2016-02-29 Angelica Pachon , Federico Polito , Laura Sacerdote

If a graph has no induced subgraph isomorphic to $H_1$ or $H_2$ then it is said to be ($H_1,H_2$)-free. Dabrowski and Paulusma found 13 open cases for the question whether the clique-width of ($H_1,H_2$)-free graphs is bounded. One of them…

Discrete Mathematics · Computer Science 2016-08-16 Andreas Brandstadt , Suhail Mahfud , Raffaele Mosca

Given a hypergraph $\Gamma=(\Omega,\mathcal{X})$ and a sequence $\mathbf{p} = (p_\omega)_{\omega\in \Omega}$ of values in $(0,1)$, let $\Omega_{\mathbf{p}}$ be the random subset of $\Omega$ obtained by keeping every vertex $\omega$…

Combinatorics · Mathematics 2019-04-18 Frank Mousset , Andreas Noever , Konstantinos Panagiotou , Wojciech Samotij

We provide new examples of the asymptotic counting for the number of subsets on groups of given size which are free of certain configurations. These examples include sets without solutions to equations in non-abelian groups, and linear…

Combinatorics · Mathematics 2016-02-08 Juanjo Rué , Oriol Serra , Lluís Vena

We consider random temporal graphs, a version of the classical Erd\H{o}s--R\'enyi random graph G(n,p) where additionally, each edge has a distinct random time stamp, and connectivity is constrained to sequences of edges with increasing time…

Probability · Mathematics 2023-06-21 Nicolas Broutin , Nina Kamčev , Gabor Lugosi

We provide large deviations estimates for the upper tail of the number of triangles in scale-free inhomogeneous random graphs where the degrees have power law tails with index $-\alpha, \alpha \in (1,2)$. We show that upper tail…

Probability · Mathematics 2024-03-25 Clara Stegehuis , Bert Zwart

It takes $n^2/4$ cliques to cover all the edges of a complete bipartite graph $K_{n/2,n/2}$, but how many cliques does it take to cover all the edges of a graph $G$ if $G$ has no $K_{t,t}$ induced subgraph? We prove that $O(|G|^{2-1/(2t)})$…

Combinatorics · Mathematics 2022-11-23 Tung Nguyen , Alex Scott , Paul Seymour , Stephan Thomasse

We prove an asymptotically tight lower bound on the average size of independent sets in a triangle-free graph on $n$ vertices with maximum degree $d$, showing that an independent set drawn uniformly at random from such a graph has expected…

Combinatorics · Mathematics 2018-01-25 Ewan Davies , Matthew Jenssen , Will Perkins , Barnaby Roberts

In this paper we consider a dynamic version of the Chung-Lu random graph in which the edges alternate between being present and absent. The main contribution concerns a technique by which one can estimate the underlying dynamics from…

Probability · Mathematics 2025-07-29 Rajat Subhra Hazra , Michel Mandjes , Jiesen Wang