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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…

Combinatorics · Mathematics 2013-12-31 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…

Combinatorics · Mathematics 2012-12-03 Qingsong Tang , Yuejian Peng , Xiangde Zhang , Cheng Zhao

Frankl and F\"uredi (1989) conjectured that the $r$-graph with $m$ edges formed by taking the first $m$ sets in the colex ordering of ${\mathbb N}^{(r)}$ has the largest graph-Lagrangian of all $r$-graphs with $m$ edges. In this paper, we…

Combinatorics · Mathematics 2014-08-26 Qingsong Tang , Yuejian Peng , Xiangde Zhang , Cheng Zhao

The Lagrangian of a hypergraph has been a useful tool in hypergraph extremal problems. In most applications, we need an upper bound for the Lagrangian of a hypergraph. Frankl and Furedi in \cite{FF} conjectured that the $r$-graph with $m$…

Combinatorics · Mathematics 2014-02-18 Qingsong Tang , Hao Peng , Cailing Wang , Yuejian Peng

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…

Combinatorics · Mathematics 2012-12-13 Yuejian Peng , Qingsong Tang , 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…

Combinatorics · Mathematics 2014-04-03 Yuejian Peng , Hegui Zhu , Yanling Zheng , Cheng Zhao

An old and well-known conjecture of Frankl and F\"{u}redi states that the Lagrangian of an $r$-uniform hypergraph with $m$ edges is maximised by an initial segment of colex. In this paper we disprove this conjecture by finding an infinite…

Combinatorics · Mathematics 2020-03-03 Vytautas Gruslys , Shoham Letzter , Natasha Morrison

A well-known conjecture of Frankl and F\"{u}redi from 1989 states that an initial segment of colex of has the largest Lagrangian of any $r$-uniform hypergraph with $m$ hyperedges. We show that this is true when $r=3$. We also give a new…

Combinatorics · Mathematics 2020-03-20 Vytautas Gruslys , Shoham Letzter , Natasha Morrison

Frankl and F\"uredi conjectured in 1989 that the maximum Lagrangian of all $r$-uniform hypergraphs of fixed size $m$ is realised by the initial segment of the colexicographic order. In particular, in the principal case $m=\binom{t}{r}$…

Combinatorics · Mathematics 2017-10-11 Mykhaylo Tyomkyn

Frankl and F\"uredi conjectured in 1989 that the maximum Lagrangian of all $r$-uniform hypergraphs of fixed size $m$ is realized by the minimum hypergraph $C_{r,m}$ under the colexicographic order. In this paper, we prove a weaker version…

Combinatorics · Mathematics 2018-06-29 Hui Lei , Linyuan Lu , Yuejian Peng

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…

Combinatorics · Mathematics 2013-11-07 Qingsong Tang , Yuejian Peng , Xiangde Zhang , Cheng zhao

Frankl and F\"uredi conjectured in 1989 that the maximum Lagrangian, denoted by $\lambda_r(m)$, among all $r$-uniform hypergraphs of fixed size $m$ is achieved by the minimum hypergraph $C_{r,m}$ under the colexicographic order. We say $m$…

Combinatorics · Mathematics 2018-07-02 Hui Lei , Linyuan Lu

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…

Combinatorics · Mathematics 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…

Combinatorics · Mathematics 2013-12-30 Qingsong Tang , Yuejian Peng , Xiangde Zhang , 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 1965. This connection and its extensions were applied in Tur\'{a}n problems of graphs and uniform…

Combinatorics · Mathematics 2013-11-01 Ran Gu , Xueliang Li , Yuejian Peng , Yongtang Shi

Recently Cutler and Radcliffe proved that the graph on $n$ vertices with maximum degree at most $r$ having the most cliques is a disjoint union of $\lfloor n/(r+1)\rfloor$ cliques of size $r+1$ together with a clique on the remainder of the…

Combinatorics · Mathematics 2021-02-19 Rachel Kirsch , A. J. Radcliffe

We study the maximum number of $r$-vertex cliques in $(r-1)$-uniform hypergraphs not containing complete $r$-partite hypergraphs $K_r^{(r-1)}(a_1, \dots, a_r)$. By using the hypergraph removal lemma, we show that this maximum is $o( n^{r -…

Combinatorics · Mathematics 2025-06-12 Ayush Basu , Vojtech Rodl , Yi Zhao

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…

Combinatorics · Mathematics 2018-11-01 Yuejian Peng , Zilong Yan

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…

Combinatorics · Mathematics 2013-12-17 Yuejian Peng , Hao Peng , Qingsong Tang , Cheng Zhao

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

Combinatorics · Mathematics 2022-09-28 Zilong Yan , Yuejian Peng
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