Degrees in oriented hypergraphs and sparse Ramsey theory
Combinatorics
2013-12-02 v2
Abstract
Let be an -uniform hypergraph. When is it possible to orient the edges of in such a way that every -set of vertices has some -degree equal to ? (The -degrees generalise for sets of vertices what in-degree and out-degree are for single vertices in directed graphs.) Caro and Hansberg asked if the obvious Hall-type necessary condition is also sufficient. Our main aim is to show that this is true for large (for given ), but false in general. Our counterexample is based on a new technique in sparse Ramsey theory that may be of independent interest.
Cite
@article{arxiv.1311.7082,
title = {Degrees in oriented hypergraphs and sparse Ramsey theory},
author = {Vytautas Gruslys},
journal= {arXiv preprint arXiv:1311.7082},
year = {2013}
}
Comments
20 pages, 3 figures