English

Vertex Ramsey problems in the hypercube

Combinatorics 2012-11-02 v1

Abstract

If we 2-color the vertices of a large hypercube what monochromatic substructures are we guaranteed to find? Call a set S of vertices from Q_d, the d-dimensional hypercube, Ramsey if any 2-coloring of the vertices of Q_n, for n sufficiently large, contains a monochromatic copy of S. Ramsey's theorem tells us that for any r \geq 1 every 2-coloring of a sufficiently large r-uniform hypergraph will contain a large monochromatic clique (a complete subhypergraph): hence any set of vertices from Q_d that all have the same weight is Ramsey. A natural question to ask is: which sets S corresponding to unions of cliques of different weights from Q_d are Ramsey? The answer to this question depends on the number of cliques involved. In particular we determine which unions of 2 or 3 cliques are Ramsey and then show, using a probabilistic argument, that any non-trivial union of 39 or more cliques of different weights cannot be Ramsey. A key tool is a lemma which reduces questions concerning monochromatic configurations in the hypercube to questions about monochromatic translates of sets of integers.

Keywords

Cite

@article{arxiv.1211.0168,
  title  = {Vertex Ramsey problems in the hypercube},
  author = {John Goldwasser and John Talbot},
  journal= {arXiv preprint arXiv:1211.0168},
  year   = {2012}
}

Comments

26 pages, 3 figures

R2 v1 2026-06-21T22:31:34.226Z