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For a bipartite graph $H$, its linear threshold is the smallest real number $\sigma$ such that every bipartite graph $G = (U \sqcup V, E)$ with unbalanced parts $|V| \gtrsim |U|^\sigma$ and without a copy of $H$ must have a linear number of…

组合数学 · 数学 2025-06-16 Lili Ködmön , Anqi Li , Ji Zeng

The problem of Zarankiewicz asks for the maximum number of edges in a bipartite graph on $n$ vertices which does not contain the complete bipartite graph $K_{k,k}$ as a subgraph. A classical theorem due to K\H{o}v\'ari, S\'os, and Tur\'an…

组合数学 · 数学 2021-04-05 Oliver Janzer , Cosmin Pohoata

The classical Zarankiewicz's problem asks for the maximum number of edges in a bipartite graph on $n$ vertices which does not contain the complete bipartite graph $K_{t,t}$. In one of the cornerstones of extremal graph theory, K\H{o}v\'ari…

组合数学 · 数学 2024-09-04 Chaya Keller , Shakhar Smorodinsky

The hypergraph Zarankiewicz's problem, introduced by Erd\H{o}s in 1964, asks for the maximum number of hyperedges in an $r$-partite hypergraph with $n$ vertices in each part that does not contain a copy of $K_{t,t,\ldots,t}$. Erd\H{o}s…

组合数学 · 数学 2025-09-12 Timothy M. Chan , Chaya Keller , Shakhar Smorodinsky

The classical Zarankiewicz problem, which concerns the maximum number of edges in a bipartite graph without a forbidden complete bipartite subgraph, motivates a direct analogue for hypergraphs. Let $K_{s_1,\ldots, s_r}$ be the complete…

组合数学 · 数学 2025-10-17 Guorong Gao , Jianfeng Hou , Shuping Huang , Hezhi Wang

The Zarankiewicz problem, a cornerstone problem in extremal graph theory, asks for the maximum number of edges in an $n$-vertex graph that does not contain the complete bipartite graph $K_{s,s}$. While the problem remains widely open in the…

组合数学 · 数学 2025-07-01 Zach Hunter , Aleksa Milojević , Istvan Tomon , Benny Sudakov

A bipartite graph $G$ is semi-algebraic in $\mathbb{R}^d$ if its vertices are represented by point sets $P,Q \subset \mathbb{R}^d$ and its edges are defined as pairs of points $(p,q) \in P\times Q$ that satisfy a Boolean combination of a…

组合数学 · 数学 2015-11-24 Jacob Fox , János Pach , Adam Sheffer , Andrew Suk , Joshua Zahl

Zarankiewicz's problem asks for the largest possible number of edges in a graph that does not contain a $K_{u,u}$ subgraph for a fixed positive integer $u$. Recently, Fox, Pach, Sheffer, Sulk and Zahl considered this problem for…

组合数学 · 数学 2018-10-02 Thao Do

Let $F$ be a graph, $k \geq 2$ be an integer, and write $\mathrm{ex}_{ \chi \leq k } (n , F)$ for the maximum number of edges in an $n$-vertex graph that is $k$-partite and has no subgraph isomorphic to $F$. The function $\mathrm{ex}_{ \chi…

组合数学 · 数学 2019-01-23 Michael Tait , Craig Timmons

For positive integers $s$, $t$, $m$ and $n$, the Zarankiewicz number $Z_{s,t}(m,n)$ is defined to be the maximum number of edges in a bipartite graph with parts of sizes $m$ and $n$ that has no complete biparitite subgraph containing $s$…

组合数学 · 数学 2024-04-11 Guangzhou Chen , Daniel Horsley , Adam Mammoliti

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…

历史与综述 · 数学 2025-03-18 Shakhar Smorodinsky

Hansen et. al. used the computer programm AutoGraphiX to study the differences between the Szeged index $Sz(G)$ and the Wiener index $W(G)$, and between the revised Szeged index $Sz^*(G)$ and the Wiener index for a connected graph $G$. They…

组合数学 · 数学 2012-12-10 Lily Chen , Xueliang Li , Mengmeng Liu

Given a family $\mathcal{F}$ of bipartite graphs, the {\it Zarankiewicz number} $z(m,n,\mathcal{F})$ is the maximum number of edges in an $m$ by $n$ bipartite graph $G$ that does not contain any member of $\mathcal{F}$ as a subgraph (such…

组合数学 · 数学 2023-01-11 Tao Jiang , Sean Longbrake , Jie Ma

An identifying code $C$ of a graph $G$ is a dominating set of $G$ such that any two distinct vertices of $G$ have distinct closed neighbourhoods within $C$. These codes have been widely studied for over two decades. We give an improvement…

组合数学 · 数学 2022-11-14 Florent Foucaud , Tuomo Lehtilä

The first multiplicative Zagreb index of a graph $G$ is the product of the square of every vertex degree, while the second multiplicative Zagreb index is the product of the degree of each edge over all edges. In our work, we explore the…

组合数学 · 数学 2017-04-28 Chunxiang Wang , Jia-Bao Liu , Shaohui Wang

We establish new lower bounds for the Tur\'an and Zarankiewicz numbers of certain apex partite hypergraphs. Given a $(d-1)$-partite $(d-1)$-uniform hypergraph $\mathcal{H}$, let $\mathcal{H}(k)$ be the $d$-partite $d$-uniform hypergraph…

组合数学 · 数学 2025-10-10 Qiyuan Chen , Hong Liu , Ke Ye

Let $G$ be a simple graph with $2n$ vertices and a perfect matching. We denote by $f(G)$ and $F(G)$ the minimum and maximum forcing number of $G$, respectively. Hetyei obtained that the maximum number of edges of graphs $G$ with a unique…

组合数学 · 数学 2022-11-23 Qianqian Liu , Heping Zhang

Bipartite Ramsey numbers is the smallest size of a complete bipartite graph $K_{N,N}$ such that every edge-coloring with a given number of colors inevitably yields a monochromatic copy of a prescribed bipartite graph. While exact values…

组合数学 · 数学 2026-04-29 Meng Ji

Ferrer dimension, along with the order dimension, is a standard dimensional concept for bipartite graphs. In this paper, we prove that a graph is of Ferrer dimension three (equivalent to the intersection bigraph of orthants and points in…

组合数学 · 数学 2025-10-24 Parinya Chalermsook , Ly Orgo , Minoo Zarsav

The Zarankiewicz number $z(m,n;s,t)$ is the maximum number of edges in a subgraph of $K_{m,n}$ that does not contain $K_{s,t}$ as a subgraph. The bipartite Ramsey number $b(n_1, \cdots, n_k)$ is the least positive integer $b$ such that any…

组合数学 · 数学 2021-06-29 Janusz Dybizbański , Tomasz Dzido , Stanisław Radziszowski
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