Large monochromatic components in 3-edge-colored Steiner triple systems
Abstract
It is known that in any -coloring of the edges of a complete -uniform hypergraph, there exists a spanning monochromatic component. Given a Steiner triple system on vertices, what is the largest monochromatic component one can guarantee in an arbitrary 3-coloring of the edges? Gy\'arf\'as proved that is an absolute lower bound and that this lower bound is best possible for infinitely many . On the other hand, we prove that for almost all Steiner triple systems the lower bound is actually . We obtain this result as a consequence of a more general theorem which shows that the lower bound depends on the size of a largest \emph{3-partite hole} (that is, sets with such that no edge intersects all of ) in the Steiner triple system (Gy\'arf\'as previously observed that the upper bound depends on this parameter). Furthermore, we show that this lower bound is tight unless the coloring has a particular structure. We also suggest a variety of other Ramsey problems in the setting of Steiner triple systems.
Cite
@article{arxiv.1908.00837,
title = {Large monochromatic components in 3-edge-colored Steiner triple systems},
author = {Louis DeBiasio and Michael Tait},
journal= {arXiv preprint arXiv:1908.00837},
year = {2020}
}
Comments
Updated to address referee comments; to appear in Journal of Combinatorial Designs