English

Local resilience of an almost spanning $k$-cycle in random graphs

Combinatorics 2018-08-31 v2

Abstract

The famous P\'{o}sa-Seymour conjecture, confirmed in 1998 by Koml\'{o}s, S\'{a}rk\"{o}zy, and Szemer\'{e}di, states that for any k2k \geq 2, every graph on nn vertices with minimum degree kn/(k+1)kn/(k + 1) contains the kk-th power of a Hamilton cycle. We extend this result to a sparse random setting. We show that for every k2k \geq 2 there exists C>0C > 0 such that if pC(logn/n)1/kp \geq C(\log n/n)^{1/k} then w.h.p. every subgraph of a random graph Gn,pG_{n, p} with minimum degree at least (k/(k+1)+o(1))np(k/(k + 1) + o(1))np, contains the kk-th power of a cycle on at least (1o(1))n(1 - o(1))n vertices, improving upon the recent results of Noever and Steger for k=2k = 2, as well as Allen et al. for k3k \geq 3. Our result is almost best possible in three ways: for pn1/kp \ll n^{-1/k} the random graph Gn,pG_{n, p} w.h.p. does not contain the kk-th power of any long cycle; there exist subgraphs of Gn,pG_{n, p} with minimum degree (k/(k+1)+o(1))np(k/(k + 1) + o(1))np and Ω(p2)\Omega(p^{-2}) vertices not belonging to triangles; there exist subgraphs of Gn,pG_{n, p} with minimum degree (k/(k+1)o(1))np(k/(k + 1) - o(1))np which do not contain the kk-th power of a cycle on (1o(1))n(1 - o(1))n vertices.

Keywords

Cite

@article{arxiv.1709.03901,
  title  = {Local resilience of an almost spanning $k$-cycle in random graphs},
  author = {Nemanja Škorić and Angelika Steger and Miloš Trujić},
  journal= {arXiv preprint arXiv:1709.03901},
  year   = {2018}
}

Comments

24 pages; small updates to the paper after anonymous reviewers' reports