English

Factors and loose Hamilton cycles in sparse pseudo-random hypergraphs

Combinatorics 2021-08-11 v2

Abstract

We investigate the emergence of spanning structures in sparse pseudo-random kk-uniform hypergraphs, using the following comparatively weak notion of pseudo-randomness. A kk-uniform hypergraph HH on nn vertices is called (p,α,ϵ)(p,\alpha,\epsilon)-pseudo-random if for all (not necessarily disjoint) vertex subsets A1,,AkV(H)A_1,\dots, A_k{\subseteq} V(H) with A1Akαnk|A_1|\cdots |A_k|{\geq}\alpha n^{k} we have e(A1,,Ak)=(1±ϵ)pA1Ak.e(A_1,\dots, A_k)=(1\pm\epsilon)p |A_1|\cdots |A_k|. For any linear kk-uniform FF we provide a bound on α=α(n)\alpha=\alpha(n) in terms of p=p(n)p=p(n) and FF, such that (under natural divisibility assumptions on nn) any kk-uniform (p,α,o(1))\big(p,\alpha, o(1)\big)-pseudo-random nn-vertex hypergraph HH with a mild minimum vertex degree condition contains an FF-factor. The approach also enables us to establish the existence of loose Hamilton cycles in sufficiently pseudo-random hypergraphs and all results imply corresponding bounds for stronger notions of hypergraph pseudo-randomness such as jumbledness or large spectral gap. As a consequence, (p,α,o(1))\big(p,\alpha, o(1)\big)-pseudo-random kk-graphs as above contain: (i)(i) a perfect matching if α=o(pk)\alpha=o(p^{k}) and (ii)(ii) a loose Hamilton cycle if α=o(pk1)\alpha=o(p^{k-1}). This extends the works of Lenz--Mubayi, and Lenz--Mubayi--Mycroft who studied the analogous problems in the dense setting.

Keywords

Cite

@article{arxiv.2001.07254,
  title  = {Factors and loose Hamilton cycles in sparse pseudo-random hypergraphs},
  author = {Hiep Hàn and Jie Han and Patrick Morris},
  journal= {arXiv preprint arXiv:2001.07254},
  year   = {2021}
}

Comments

Updated according to reviewer comments, to appear in RSA (Random Structures & Algorithms), 23 pages, 3 figures, an extended abstract appeared in the conference proceedings of SODA 2020, pp. 702-717

R2 v1 2026-06-23T13:15:55.397Z