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Packing Loose Hamilton Cycles

Published online by Cambridge University Press:  01 August 2017

Abstract

A subset C of edges in a k-uniform hypergraph H is a loose Hamilton cycle if C covers all the vertices of H and there exists a cyclic ordering of these vertices such that the edges in C are segments of that order and such that every two consecutive edges share exactly one vertex. The binomial random k-uniform hypergraph Hkn,p has vertex set [n] and an edge set E obtained by adding each k-tuple e ∈ ($\binom{[n]}{k}$) to E with probability p, independently at random.

Here we consider the problem of finding edge-disjoint loose Hamilton cycles covering all but o(|E|) edges, referred to as the packing problem. While it is known that the threshold probability of the appearance of a loose Hamilton cycle in Hkn,p is

$p=\Theta\biggl(\frac{\log n}{n^{k-1}}\biggr),$
the best known bounds for the packing problem are around p = polylog(n)/n. Here we make substantial progress and prove the following asymptotically (up to a polylog(n) factor) best possible result: for p ≥ logCn/nk−1, a random k-uniform hypergraph Hkn,p with high probability contains
$N:=(1-o(1))\frac{\binom{n}{k}p}{n/(k-1)}$
edge-disjoint loose Hamilton cycles.

Our proof utilizes and modifies the idea of ‘online sprinkling’ recently introduced by Vu and the first author.

Type
Paper
Copyright
Copyright © Cambridge University Press 2017 

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