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This paper presents a quantum algorithm for triangle finding over sparse graphs that improves over the previous best quantum algorithm for this task by Buhrman et al. [SIAM Journal on Computing, 2005]. Our algorithm is based on the recent…

Quantum Physics · Physics 2021-10-05 François Le Gall , Shogo Nakajima

Every $n$-vertex planar triangle-free graph with maximum degree at most $3$ has an independent set of size at least $\frac{3}{8}n$. This was first conjectured by Albertson, Bollob\'as and Tucker, and was later proved by Heckman and Thomas.…

Combinatorics · Mathematics 2020-07-15 Wouter Cames van Batenburg , Jan Goedgebeur , Gwenaël Joret

One of the most fundamental results in graph theory is Mantel's theorem which determines the maximum number of edges in a triangle-free graph of order $n$. Recently a colorful variant of this problem has been solved. In such a variant we…

Combinatorics · Mathematics 2023-08-08 Sebastian Babiński , Andrzej Grzesik , Magdalena Prorok

In 1994, Alon construct a triangle-free $(n,d,\lambda)$-graph with $d = \Omega(n^{2/3})$ and $\lambda = O(d^{1/2})$ for an exponentially increasing sequence of integers $n$. Using his ingenious construction, we deduce that there exist…

Combinatorics · Mathematics 2024-01-05 Jaehoon Kim , Hyunwoo Lee

We present an essentially tight bound for the Ramsey-Tur\'an problem for 4-cliques without using the Regularity lemma. This enables us to substantially extend the range in which one has the tight bound for the number of edges in $K_4$-free…

Combinatorics · Mathematics 2025-03-04 Béla Csaba

We give a simple proof of the recent remarkable exponential improvement for Ramsey lower bounds, obtained by Ma, Shen and Xie. Our key ingredient is an alternative construction based on Gaussian random graphs, which allows us to simplify…

Combinatorics · Mathematics 2026-05-19 Zach Hunter , Aleksa Milojević , Benny Sudakov

The weighted Ramsey number, ${\rm wR}(n,k)$, is the minimum $q$ such that there is an assignment of nonnegative real numbers (weights) to the edges of $K_n$ with the total sum of the weights equal to ${n\choose 2}$ and there is a Red/Blue…

Combinatorics · Mathematics 2016-05-23 Maria Axenovich , Ryan Martin

According to a study by Erd\H{o}s et al. in 1975, the anti-Ramsey number of a graph \(G\), denoted as \(AR(n, G)\), is defined as the maximum number of colors that can be used in an edge-coloring of the complete graph \(K_n\) without…

Combinatorics · Mathematics 2025-12-12 Ali Ghalavand , Qing Jie , Zemin Jin , Xueliang Li , Linshu Pan

Motivated by the investigation of sharpness of thresholds for Ramsey properties in random graphs, Friedgut, Kohayakawa, R\"odl, Ruci\'nski and Tetali introduced two variants of a single-player game whose goal is to colour the edges of…

Combinatorics · Mathematics 2023-05-05 Yahav Alon , Patrick Morris , Wojciech Samotij

Building upon previous works by Conlon-Ferber and Wigderson, Sawin showed a few years ago that upper bounds on the minimum density of independent sets in a $K_t$-free $G$ can be used to provide lower bounds for multicolor Ramsey numbers. In…

Combinatorics · Mathematics 2026-01-22 Marcelo Campos , Cosmin Pohoata

Let $F_{3,3}$ be the 3-graph on 6 vertices, labelled abcxyz, and 10 edges, one of which is abc, and the other 9 of which are all triples that contain 1 vertex from abc and 2 vertices from xyz. We show that for all $n \ge 6$, the maximum…

Combinatorics · Mathematics 2011-02-11 Peter Keevash , Dhruv Mubayi

We study the random planar graph process introduced by Gerke, Schlatter, Steger, and Taraz [The random planar graph process, Random Structures Algorithms 32 (2008), no. 2, 236--261; MR2387559]: Begin with an empty graph on $n$ vertices,…

Combinatorics · Mathematics 2022-06-14 Mihyun Kang , Michael Missethan

A celebrated result of Johansson in graph theory states that every triangle-free graph of maximum degree $\Delta$ can be properly colored with $O(\Delta/\ln\Delta)$ colors, improving upon the "greedy bound" of $\Delta+1$ coloring in general…

Data Structures and Algorithms · Computer Science 2026-04-23 Sepehr Assadi , Helia Yazdanyar

We develop tail estimates for the number of edges in a Chung-Lu random graph with regularly varying weight distribution. Our results show that the most likely way to have an unusually large number of edges is through the presence of one or…

Probability · Mathematics 2023-12-05 Clara Stegehuis , Bert Zwart

In 2016, Dowden initiated the study of planar Tur\'an-type problems, which has since attracted considerable attention. Recently, Bekos et al. proved that every $K_3$-free $1$-planar graph on $n\ge 4$ vertices has at most $3n-6$ edges. In…

Combinatorics · Mathematics 2026-04-27 Licheng Zhang , Yuanqiu Huang , Fengming Dong

Let K_4 denote the complete 3-uniform hypergraph on 4 vertices. Ajtai, Erd\H{o}s, Koml\'os, and Szemer\'edi (1981) asked if there is a function \omega(d) tending to infinity such that every 3-uniform, K_4-free hypergraph N vertices and…

Combinatorics · Mathematics 2014-07-24 Jeff Cooper , Dhruv Mubayi

Alon, Balogh, Keevash and Sudakov proved that the $(k-1)$-partite Tur\'an graph maximizes the number of distinct $r$-edge-colorings with no monochromatic $K_k$ for all fixed $k$ and $r=2,3$, among all $n$-vertex graphs. In this paper, we…

Combinatorics · Mathematics 2017-04-25 József Balogh , Hong Liu , Maryam Sharifzadeh

We revisit the algorithmic problem of finding a triangle in a graph (\textsc{Triangle Detection}), and examine its relation to other problems such as \textsc{3Sum}, \textsc{Independent Set}, and \textsc{Graph Coloring}. We obtain several…

Data Structures and Algorithms · Computer Science 2024-02-13 Adrian Dumitrescu

We introduce a graph Ramsey game called Ramsey, Paper, Scissors. This game has two players, Proposer and Decider. Starting from an empty graph on $n$ vertices, on each turn Proposer proposes a potential edge and Decider simultaneously…

Combinatorics · Mathematics 2020-06-24 Jacob Fox , Xiaoyu He , Yuval Wigderson

A set of vertices $X\subseteq V$ in a simple graph $G(V,E)$ is irredundant if each vertex $x\in X$ is either isolated in the induced subgraph $G[X]$ or else has a private neighbor $y\in V\setminus X$ that is adjacent to $x$ and to no other…

Combinatorics · Mathematics 2026-04-23 Meng Ji , Yaping Mao , Ingo Schiermeyer