English

Catching a robber on a random $k$-uniform hypergraph

Combinatorics 2024-04-29 v2

Abstract

The game of \emph{Cops and Robber} is usually played on a graph, where a group of cops attempt to catch a robber moving along the edges of the graph. The \emph{cop number} of a graph is the minimum number of cops required to win the game. An important conjecture in this area, due to Meyniel, states that the cop number of an nn-vertex connected graph is O(n)O(\sqrt{n}). In 2016, Pra{\l}at and Wormald [Meyniel's conjecture holds for random graphs, Random Structures Algorithms. 48 (2016), no. 2, 396-421. MR3449604] showed that this conjecture holds with high probability for random graphs above the connectedness threshold. Moreoever, {\L}uczak and Pra{\l}at [Chasing robbers on random graphs: Zigzag theorem, Random Structures Algorithms. 37 (2010), no. 4, 516-524. MR2760362] showed that on a log\log-scale the cop number demonstrates a surprising \emph{zigzag} behaviour in dense regimes of the binomial random graph G(n,p)G(n,p). In this paper, we consider the game of Cops and Robber on a hypergraph, where the players move along hyperedges instead of edges. We show that with high probability the cop number of the kk-uniform binomial random hypergraph Gk(n,p)G^k(n,p) is O(nklogn)O\left(\sqrt{\frac{n}{k}}\, \log n \right) for a broad range of parameters pp and kk and that on a log\log-scale our upper bound on the cop number arises as the minimum of \emph{two} complementary zigzag curves, as opposed to the case of G(n,p)G(n,p). Furthermore, we conjecture that the cop number of a connected kk-uniform hypergraph on nn vertices is O(nk)O\left(\sqrt{\frac{n}{k}}\,\right).

Keywords

Cite

@article{arxiv.2307.15512,
  title  = {Catching a robber on a random $k$-uniform hypergraph},
  author = {Joshua Erde and Mihyun Kang and Florian Lehner and Bojan Mohar and Dominik Schmid},
  journal= {arXiv preprint arXiv:2307.15512},
  year   = {2024}
}

Comments

21 pages

R2 v1 2026-06-28T11:42:49.358Z