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A celebrated unresolved conjecture of Erd\H{o}s and Hajnal states that for every undirected graph $H$ there exists $\epsilon(H)>0$ such that every undirected graph on $n$ vertices that does not contain $H$ as an induced subgraph contains a…

Combinatorics · Mathematics 2015-08-21 Eli Berger , Krzysztof Choromanski , Maria Chudnovsky

A celebrated unresolved conjecture of Erd\"{o}s and Hajnal states that for every undirected graph $H$ there exists $ \epsilon(H) > 0 $ such that every undirected graph on $ n $ vertices that does not contain $H$ as an induced subgraph…

Combinatorics · Mathematics 2022-08-10 Salman Ghazal , Soukaina Zayat

The celebrated Erd\"{o}s-Hajnal conjecture states that for every undirected graph $H$ there exists $ \epsilon(H) > 0 $ such that every undirected graph on $ n $ vertices that does not contain $H$ as an induced subgraph contains a clique or…

Combinatorics · Mathematics 2022-08-11 Soukaina Zayat , Salman Ghazal

Erd\"{o}s-Hajnal conjecture states that for every undirected graph $H$ there exists $ \epsilon(H) > 0 $ such that every undirected graph on $ n $ vertices that does not contain $H$ as an induced subgraph contains a clique or a stable set of…

Combinatorics · Mathematics 2022-08-10 Soukaina Zayat , Salman Ghazal

The Erd\H{o}s-Hajnal conjecture states that for every given undirected graph $H$ there exists a constant $c(H)>0$ such that every graph $G$ that does not contain $H$ as an induced subgraph contains a clique or a stable set of size at least…

Combinatorics · Mathematics 2014-10-28 Krzysztof Choromanski

The Erd\H{o}s-Hajnal Conjecture states that for every $H$ there exists a constant $\epsilon(H)>0$ such that every graph $G$ that does not contain $H$ as an induced subgraph contains a clique or a stable set of size at least…

Combinatorics · Mathematics 2014-10-28 Krzysztof Choromanski

A conjecture of Alon, Pach and Solymosi, which is equivalent to the celebrated Erd\H{o}s-Hajnal Conjecture, states that for every tournament $S$ there exists $\epsilon(S)>0$ such that if $T$ is an $n$-vertex tournament that does not…

Combinatorics · Mathematics 2021-09-15 Eli Berger , Krzysztof Choromanski , Maria Chudnovsky , Shira Zerbib

An equivalent directed version of the celebrated unresolved conjecture of Erdos and Hajnal proposed by Alon, Pack, and Solymosi states that for every tournament H there exists epsilon(H)>0 such that every H-free n-vertex tournament T…

Combinatorics · Mathematics 2023-01-31 Soukaina Zayat

The Erd\"os-Hajnal conjecture states that for every graph $H$, there exists a constant $\delta(H) > 0$ such that every graph $G$ with no induced subgraph isomorphic to $H$ has either a clique or a stable set of size at least…

Combinatorics · Mathematics 2016-06-29 Maria Chudnovsky

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

The Erd\H{o}s-Hajnal conjecture is one of the most classical and well-known problems in extremal and structural combinatorics dating back to 1977. It asserts that in stark contrast to the case of a general $n$-vertex graph if one imposes…

Combinatorics · Mathematics 2023-10-27 Pablo Blanco , Matija Bucić

Erd\H{o}s and Hajnal conjectured that for every graph $H$, there exists $c>0$ such that every $H$-free graph $G$ has a clique or a stable set of size at least $|G|^c$ (a graph is $H$-free if it has no induced subgraph isomorphic to $H$).…

Combinatorics · Mathematics 2026-04-21 Tung Nguyen , Alex Scott , Paul Seymour

We prove that there exists $C>0$ such that $\epsilon(H) \geq \frac{C}{|H|^{5}\log(|H|)}$, where $\epsilon(H)$ is the Erd\H{o}s-Hajnal coefficient of the tournament $H$, for every prime tournament $H$ for which the celebrated…

Combinatorics · Mathematics 2014-10-28 Krzysztof Choromanski

An equivalent directed version of the celebrated unresolved conjecture of Erdos and Hajnal proposed by Alon et al. states that for every tournament H there exists epsilon(H) > 0 such that every H-free n-vertex tournament T contains a…

Combinatorics · Mathematics 2022-09-20 Soukaina Zayat

We prove that for every graph $H$, there exists $\varepsilon>0$ such that every $n$-vertex graph with no vertex-minors isomorphic to $H$ has a pair of disjoint sets $A$, $B$ of vertices such that $|A|, |B|\ge \varepsilon n$ and $A$ is…

Combinatorics · Mathematics 2018-10-05 Maria Chudnovsky , Sang-il Oum

The celebrated Erdos-Hajnal conjecture states that for every $n$-vertex undirected graph $H$ there exists $\eps(H)>0$ such that every graph $G$ that does not contain $H$ as an induced subgraph contains a clique or an independent set of size…

Combinatorics · Mathematics 2015-08-06 Krzysztof Choromanski , Dvir Falik , Anita Liebenau , Viresh Patel , Marcin Pilipczuk

Erd\H{o}s and Hajnal conjectured that, for every graph $H$, there exists a constant $c_H$ such that every graph $G$ on $n$ vertices which does not contain any induced copy of $H$ has a clique or a stable set of size $n^{c_H}$. We prove that…

Discrete Mathematics · Computer Science 2014-08-12 Marthe Bonamy , Nicolas Bousquet , Stéphan Thomassé

We prove a conjecture of Kim and Oum that every proper pivot-minor-closed class of graphs has the strong Erd\H{o}s-Hajnal property. More precisely, for every graph $H$, there exists $\epsilon > 0$ such that every $n$-vertex graph with no…

Combinatorics · Mathematics 2025-04-09 James Davies

The Erdos-Hajnal conjecture says that for every graph H there exists c>0 such that every graph G not containing H as an induced subgraph has a clique or stable set of cardinality at least |G|^c. We prove that this is true when H is a cycle…

Combinatorics · Mathematics 2021-02-10 Maria Chudnovsky , Alex Scott , Paul Seymour , Sophie Spirkl

We prove the Erd\H{o}s-Hajnal conjecture for the five-vertex path $P_5$; that is, there exists $c>0$ such that every $n$-vertex graph with no induced $P_5$ has a clique or stable set of size at least $n^c$. This completes the verification…

Combinatorics · Mathematics 2026-02-25 Tung Nguyen , Alex Scott , Paul Seymour
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