An irrational Turán density via hypergraph Lagrangian densities
The electronic journal of combinatorics, Tome 29 (2022) no. 3
Baber and Talbot asked whether there is an irrational Turán density of a single hypergraph. In this paper, we show that the Lagrangian density of a 4-uniform matching of size 3 is an irrational number. Sidorenko showed that the Lagrangian density of an r-uniform hypergraph F is the same as the Turán density of the extension of F. Therefore, our result gives a positive answer to the question of Baber and Talbot. We also determine the Lagrangian densities of a class of r-uniform hypergraphs on n vertices with θ(n2) edges. As far as we know, for every hypergraph F with known hypergraph Lagrangian density, the number of edges in F is less than the number of its vertices.
DOI :
10.37236/10645
Classification :
05D05, 05C65, 05C30
Mots-clés : maximal number of edges, Turán problem
Mots-clés : maximal number of edges, Turán problem
Affiliations des auteurs :
Biao Wu  1
@article{10_37236_10645,
author = {Biao Wu},
title = {An irrational {Tur\'an} density via hypergraph {Lagrangian} densities},
journal = {The electronic journal of combinatorics},
year = {2022},
volume = {29},
number = {3},
doi = {10.37236/10645},
zbl = {1498.05270},
url = {http://geodesic.mathdoc.fr/articles/10.37236/10645/}
}
Biao Wu. An irrational Turán density via hypergraph Lagrangian densities. The electronic journal of combinatorics, Tome 29 (2022) no. 3. doi: 10.37236/10645
Cité par Sources :