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In 1965, Motzkin and Straus established a remarkable connection between the order of a maximum clique and the Lagrangian of a graph and provided a new proof of Tur\'an's theorem using the connection. The connection of Lagrangians and…

组合数学 · 数学 2013-12-17 Yuejian Peng , Hao Peng , Qingsong Tang , Cheng Zhao

A remarkable connection between the order of a maximum clique and the Lagrangian of a graph was established by Motzkin and Straus in [7]. This connection and its extensions were successfully employed in optimization to provide heuristics…

组合数学 · 数学 2012-12-13 Yuejian Peng , Qingsong Tang , Cheng Zhao

A remarkable connection between the order of a maximum clique and the Graph-Lagrangian of a graph was established by Motzkin and Straus in 1965. This connection and its extension were useful in both combinatorics and optimization. Since…

组合数学 · 数学 2014-05-27 Yuejian Peng , Yuping Yao

Motzkin and Straus established a close connection between the maximum clique problem and a solution (namely graph-Lagrangians) to the maximum value of a class of homogeneous quadratic multilinear functions over the standard simplex of the…

组合数学 · 数学 2013-12-30 Qingsong Tang , Yuejian Peng , Xiangde Zhang , Cheng Zhao

There is a remarkable connection between the clique number and the Lagrangian of a 2-graph proved by Motzkin and Straus in 1965. It is useful in practice if similar results hold for hypergraphs. However the obvious generalization of Motzkin…

组合数学 · 数学 2013-12-31 Qingsong Tang , Yuejian Peng , Xiangde Zhang , Cheng Zhao

There is a remarkable connection between the maximum clique number and the Lagrangian of a graph given by T. S. Motzkin and E.G. Straus in 1965. This connection and its extensions were successfully employed in optimization to provide…

组合数学 · 数学 2014-04-03 Yuejian Peng , Hegui Zhu , Yanling Zheng , Cheng Zhao

Motzkin and Straus established a remarkable connection between the maximum clique and the Lagrangian of a graph in 1965. This connection and its extensions were successfully employed in optimization to provide heuristics for the maximum…

组合数学 · 数学 2013-11-07 Qingsong Tang , Yuejian Peng , Xiangde Zhang , Cheng zhao

In 1965, Motzkin and Straus [5] provided a new proof of Turan's theorem based on a continuous characterization of the clique number of a graph using the Lagrangian of a graph. This new proof aroused interests in the study of Lagrangians of…

组合数学 · 数学 2012-12-03 Qingsong Tang , Yuejian Peng , Xiangde Zhang , Cheng Zhao

It is conjectured by Frankl and F\"uredi that the $r$-uniform hypergraph with $m$ edges formed by taking the first $m$ sets in the colex ordering of ${\mathbb N}^{(r)}$ has the largest Lagrangian of all $r$-uniform hypergraphs with $m$…

组合数学 · 数学 2014-05-13 Qingsong Tang , Xiaojun Lu , Xiangde Zhang , Cheng Zhao

The hypergraph jump problem and the study of Lagrangians of uniform hypergraphs are two classical areas of study in the extremal graph theory. In this paper, we refine the concept of jumps to strong jumps and consider the analogous problems…

组合数学 · 数学 2014-03-06 Travis Johnston , Linyuan Lu

An $r$-uniform graph $G$ is dense if and only if every proper subgraph $G'$ of $G$ satisfies $\lambda (G') < \lambda (G)$, where $\lambda (G)$ is the Lagrangian of a hypergraph $G$. In 1980's, Sidorenko showed that $\pi(F)$, the Tur\'an…

组合数学 · 数学 2017-01-24 Biao Wu , Yuejian Peng

Unlike graphs, determining Tur\'{a}n densities of hypergraphs is known to be notoriously hard in general. The essential reason is that for many classical families of $r$-uniform hypergraphs $\mathcal{F}$, there are perhaps many…

组合数学 · 数学 2023-12-03 Jianfeng Hou , Heng Li , Guanghui Wang , Yixiao Zhang

The Lagrangian density of an $r$-uniform hypergraph $F$ is $r!$ multiplying the supremum of the Lagrangians of all $F$-free $r$-uniform hypergraphs. For an $r$-graph $H$ with $t$ vertices, it is clear that $\pi_{\lambda}(H)\ge…

组合数学 · 数学 2018-11-01 Yuejian Peng , Zilong Yan

The uniform Tur\'an density $\pi_{u}(F)$ of a $3$-uniform hypergraph (or $3$-graph) $F$ is the supremum of all $d$ such that there exist infinitely many $F$-free $3$-graphs $H$ in which every induced subhypergraph on a linearly sized vertex…

组合数学 · 数学 2026-03-12 Hao Lin , Guanghui Wang , Wenling Zhou , Yiming Zhou

In the 1980s, Erd\H{o}s and S\'os initiated the study of Tur\'an hypergraph problems with a uniformity condition on the distribution of edges, i.e., determining density thresholds for the existence of a hypergraph H in a host hypergraph…

组合数学 · 数学 2025-05-27 Daniel Král' , Filip Kučerák , Ander Lamaison , Gábor Tardos

Generalized Tur\'an problems have been a central topic of study in extremal combinatorics throughout the last few decades. One such problem, maximizing the number of cliques of a fixed order in a graph with fixed number of vertices and…

组合数学 · 数学 2021-06-10 Debsoumya Chakraborti , Da Qi Chen

We study Tur\'an-type extremal problems for distance graphs, motivated by work of Csikv\'ari, Bollob\'as, Tyomkyn, and Uzzell. We determine the maximum number of vertex pairs at distance three in an $n$-vertex graph with no triangle formed…

组合数学 · 数学 2026-05-01 Zhen He , Nika Salia , Casey Tompkins , Xiutao Zhu

The study of uniform Tur\'an densities was initiated in the 1980s by Erd\H{o}s and S\'os. Given a $3$-graph $F$, the uniform Tur\'an density of $F$, $\pi_{\therefore}(F)$, is defined as the infimum $d\in[0,1]$ such that every $3$-graph $H$…

组合数学 · 数学 2024-12-11 Dylan King , Marcelo Sales , Bjarne Schülke

In 1965, T. S. Motzkin and E. G. Straus established an elegant connection between the clique number of a graph and the global maxima of a quadratic program defined on the standard simplex. Over the years, this seminal finding has inspired a…

最优化与控制 · 数学 2024-12-24 G. Beretta , A. Torcinovich , M. Pelillo

Generalized Tur\'an problems have been a central topic of study in extremal combinatorics throughout the last few decades. One such problem is maximizing the number of cliques of size $t$ in a graph of a fixed order that does not contain…

组合数学 · 数学 2024-03-01 Debsoumya Chakraborti , Da Qi Chen
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