English

On a topological version of Pach's overlap theorem

Combinatorics 2019-11-20 v2 Algebraic Topology

Abstract

Pach showed that every d+1d+1 sets of points Q1,,Qd+1RdQ_1,\dotsc,Q_{d+1} \subset \mathbb{R}^d contain linearly-sized subsets PiQiP_i\subset Q_i such that all the transversal simplices that they span intersect. We show, by means of an example, that a topological extension of Pach's theorem does not hold with subsets of size C(logn)1/(d1)C(\log n)^{1/(d-1)}. We show that this is tight in dimension 22, for all surfaces other than S2\mathbb{S}^2. Surprisingly, the optimal bound for S2\mathbb{S}^2 in the topological version of Pach's theorem is of the order (logn)1/2(\log n)^{1/2}. We conjecture that, among higher-dimensional manifolds, spheres are similarly distinguished. This improves upon the results of B\'ar\'any, Meshulam, Nevo and Tancer.

Keywords

Cite

@article{arxiv.1708.04350,
  title  = {On a topological version of Pach's overlap theorem},
  author = {Boris Bukh and Alfredo Hubard},
  journal= {arXiv preprint arXiv:1708.04350},
  year   = {2019}
}

Comments

9 pages, 2 figures