scholarly journals The Turán Polytope

10.37236/6555 ◽  
2018 ◽  
Vol 25 (3) ◽  
Author(s):  
Annie Raymond

The Turán hypergraph problem asks to find the maximum number of $r$-edges in a $r$-uniform hypergraph on $n$ vertices that does not contain a clique of size $a$. When $r=2$, i.e., for graphs, the answer is well-known and can be found in Turán's theorem. However, when $r\ge 3$, the problem remains open. We model the problem as an integer program and call the underlying polytope the Turán polytope. We draw parallels between the latter and the stable set polytope: we show that generalized and transformed versions of the web and wheel inequalities are also facet-defining for the Turán polytope. We also show that clique inequalities and what we call doubling inequalities are facet-defining when $r=2$. These facets lead to a simple new polyhedral proof of Turán's theorem.

2007 ◽  
Vol 115 (2) ◽  
pp. 291-317 ◽  
Author(s):  
Gianpaolo Oriolo ◽  
Gautier Stauffer

10.37236/771 ◽  
2008 ◽  
Vol 15 (1) ◽  
Author(s):  
Andrzej Dudek ◽  
Vojtěch Rödl

Let $G^{(\infty)}$ be an infinite graph with the vertex set corresponding to the set of positive integers ${\Bbb N}$. Denote by $G^{(l)}$ a subgraph of $G^{(\infty)}$ which is spanned by the vertices $\{1,\dots,l\}$. As a possible extension of Turán's theorem to infinite graphs, in this paper we will examine how large $\liminf_{l\rightarrow \infty} {|E(G^{(l)})|\over l^2}$ can be for an infinite graph $G^{(\infty)}$, which does not contain an increasing path $I_k$ with $k+1$ vertices. We will show that for sufficiently large $k$ there are $I_k$–free infinite graphs with ${1\over 4}+{1\over 200} < \liminf_{l\rightarrow \infty} {|E(G^{(l)})|\over l^2}$. This disproves a conjecture of J. Czipszer, P. Erdős and A. Hajnal. On the other hand, we will show that $\liminf_{l\rightarrow \infty} {|E(G^{(l)})|\over l^2}\le{1\over 3}$ for any $k$ and such $G^{(\infty)}$.


COMBINATORICA ◽  
2019 ◽  
Vol 39 (5) ◽  
pp. 961-982 ◽  
Author(s):  
Louis Bellmann ◽  
Christian Reiher

2015 ◽  
Vol 50 ◽  
pp. 261-266 ◽  
Author(s):  
Ricardo C. Corrêa ◽  
Javier Marenco ◽  
Diego Delle Donne ◽  
Ivo Koch

2003 ◽  
Vol 23 (3) ◽  
pp. 225-234 ◽  
Author(s):  
Tibor Szabó ◽  
Van H. Vu

1999 ◽  
Vol 106 (3) ◽  
pp. 257-258
Author(s):  
William Staton

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