English

Avoiding long Berge cycles

Combinatorics 2018-05-15 v2

Abstract

Let nkr+3n\geq k\geq r+3 and H\mathcal H be an nn-vertex rr-uniform hypergraph. We show that if H>n1k2(k1r)|\mathcal H|> \frac{n-1}{k-2}\binom{k-1}{r} then H\mathcal H contains a Berge cycle of length at least kk. This bound is tight when k2k-2 divides n1n-1. We also show that the bound is attained only for connected rr-uniform hypergraphs in which every block is the complete hypergraph Kk1(r)K^{(r)}_{k-1}. We conjecture that our bound also holds in the case k=r+2k=r+2, but the case of short cycles, kr+1k\leq r+1, is different.

Keywords

Cite

@article{arxiv.1805.04195,
  title  = {Avoiding long Berge cycles},
  author = {Zoltan Furedi and Alexandr Kostochka and Ruth Luo},
  journal= {arXiv preprint arXiv:1805.04195},
  year   = {2018}
}
R2 v1 2026-06-23T01:51:33.328Z