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An $(n,s,q)$-graph is an $n$-vertex multigraph in which every $s$-set of vertices spans at most $q$ edges. Tur\'an-type questions on the maximum of the sum of the edge multiplicities in such multigraphs have been studied since the 1990s.…

Combinatorics · Mathematics 2021-12-20 A. Nicholas Day , Victor Falgas-Ravry , Andrew Treglown

Classical questions in extremal graph theory concern the asymptotics of $\operatorname{ex}(G, \mathcal{H})$ where $\mathcal{H}$ is a fixed family of graphs and $G=G_n$ is taken from a `standard' increasing sequence of host graphs $(G_1,…

Combinatorics · Mathematics 2019-03-07 Joseph Briggs , Christopher Cox

The \emph{Tur\'an function} $\ex(n,F)$ of a graph $F$ is the maximum number of edges in an $F$-free graph with $n$ vertices. The classical results of Tur\'an and Rademacher from 1941 led to the study of supersaturated graphs where the key…

Combinatorics · Mathematics 2016-11-08 Oleg Pikhurko , Zelealem B. Yilma

There are two particular $\Theta_6$-graphs - the 6-cycle graphs with a diagonal. We find the planar Tur\'an number of each of them, i.e. the maximum number of edges in a planar graph $G$ of $n$ vertices not containing the given $\Theta_6$…

Combinatorics · Mathematics 2024-07-01 David Guan , Ervin Győri , Diep Luong-Le , Felicia Wang , Mengyuan Yang

In the 1960s, Erd\H{o}s and Gallai conjectured that the edge set of every graph on n vertices can be partitioned into O(n) cycles and edges. They observed that one can easily get an O(n log n) upper bound by repeatedly removing the edges of…

Combinatorics · Mathematics 2014-05-23 David Conlon , Jacob Fox , Benny Sudakov

A classical result of Bondy and Simonovits in extremal graph theory states that if a graph on $n$ vertices contains no cycle of length $2k$ then it has at most $O(n^{1+1/k})$ edges. However, matching lower bounds are only known for…

Combinatorics · Mathematics 2018-07-18 Ervin Győri , Dániel Korándi , Abhishek Methuku , István Tomon , Casey Tompkins , Máté Vizer

Given graphs $H$ and $F$, the generalized Tur\'an number $\mathrm{ex}(n,H,F)$ is the largest number of copies of $H$ in $n$-vertex $F$-free graphs. Stability refers to the usual phenomenon that if an $n$-vertex $F$-free graph $G$ contains…

Combinatorics · Mathematics 2022-04-12 Dániel Gerbner

For a family $\mathcal{F}$ of graphs, let $ex(n,\mathcal{F})$ denote the maximum number of edges in an $n$-vertex graph which contains none of the members of $\mathcal{F}$ as a subgraph. A longstanding problem in extremal graph theory asks…

Combinatorics · Mathematics 2022-12-06 Jie Ma , Tianchi Yang

The generalized list $T$-coloring is a common generalization of many graph coloring models, including classical coloring, $L(p,q)$-labeling, channel assignment and $T$-coloring. Every vertex from the input graph has a list of permitted…

Discrete Mathematics · Computer Science 2013-12-04 Konstanty Junosza-Szaniawski , Paweł Rzążewski

Extremal Graph Theory is a very deep and wide area of modern combinatorics. It is very fast developing, and in this long but relatively short survey we select some of those results which either we feel very important in this field or which…

Combinatorics · Mathematics 2019-12-05 Miklós Simonovits , Endre Szemerédi

Determining the maximum number of edges in an intersecting hypergraph on a fixed ground set under additional constraints is one of the central topics in extremal combinatorics. In contrast, there are few results on analogous problems…

Combinatorics · Mathematics 2025-04-08 Stijn Cambie , Jaehoon Kim , Hyunwoo Lee , Hong Liu , Tuan Tran

One of the central topics in extremal graph theory is the study of the function $ex(n,H)$, which represents the maximum number of edges a graph with $n$ vertices can have while avoiding a fixed graph $H$ as a subgraph. Tur{\'a}n provided a…

History and Overview · Mathematics 2025-03-18 Shakhar Smorodinsky

For two graphs $G$ and $H$, the Tur\'{a}n number $ex(G,H)$ is the maximum number of edges in a subgraph of $G$ that contains no copy of $H$. Chen, Li, and Tu determined the Tur\'{a}n numbers $ex(K_{m,n},kK_2)$ for all $k\geq 1$ [7]. In this…

Combinatorics · Mathematics 2017-09-06 Jessica De Silva , Kristin Heysse , Adam Kapilow , Anna Schenfisch , Michael Young

A long standing open problem in extremal graph theory is to describe all graphs that maximize the number of induced copies of a path on four vertices. The character of the problem changes in the setting of oriented graphs, and becomes more…

Combinatorics · Mathematics 2020-06-12 Ilkyoo Choi , Bernard Lidický , Florian Pfender

A {\it vertex-ordered} graph is a graph equipped with a linear ordering of its vertices. A pair of independent edges in an ordered graph can exhibit one of the following three patterns: separated, nested or crossing. We say a pair of…

Combinatorics · Mathematics 2025-12-23 János Barát , Andrea Freschi , Géza Tóth

The generalized Tur\'an number for $H$ of $G$, denoted by $\ex(n,H,G)$, is the maximum number of copies of $H$ in an $n$-vertex $G$-free graph. When $H$ is an edge, $\ex(n,H,G)$ is the classical Tur\'an number $\ex(n,G)$. Let $P_k$ be the…

Combinatorics · Mathematics 2026-01-15 Yichen Wang , Ervin Győri

For a family of graphs $\cal F$, a graph $G$ is $\cal F$-free if it does not contain a member of $\cal F$ as a subgraph. The Tur\'an number $\textrm{ex}(n,{\cal F})$ is the maximum number of edges in an $n$-vertex graph which is $\cal…

Combinatorics · Mathematics 2024-12-13 Chunyang Dou , Fu-tao Hu , Xing Peng

The Tur\'{a}n number of a graph $H$ is the maximum number of edges in any graph of order $n$ that does not contain $H$ as a subgraph. In 1959, Erd\H os and Gallai obtained a sharp upper bound of Tur\'{a}n numbers for a path of arbitrary…

Combinatorics · Mathematics 2025-11-04 Miao Dong , Bo Ning , Long-Tu Yuan , Xiao-Dong Zhang

Confirming a conjecture of Vera T. S\'os in a very strong sense, we give a complete solution to Tur\'an's hypergraph problem for the Fano plane. That is we prove for $n\ge 8$ that among all $3$-uniform hypergraphs on $n$ vertices not…

Combinatorics · Mathematics 2020-03-24 Louis Bellmann , Christian Reiher

For graphs $H$ and $F$, the generalized Tur\'an number $ex(n,H,F)$ is the largest number of copies of $H$ in an $F$-free graph on $n$ vertices. We consider this problem when both $H$ and $F$ have at most four vertices. We give sharp results…

Combinatorics · Mathematics 2020-06-30 Dániel Gerbner