English

Between 2- and 3-colorability

Combinatorics 2014-04-22 v1

Abstract

We consider the question of the existence of homomorphisms between Gn,pG_{n,p} and odd cycles when p=c/n,1<c4p=c/n,\,1<c\leq 4. We show that for any positive integer \ell, there exists ϵ=ϵ()\epsilon=\epsilon(\ell) such that if c=1+ϵc=1+\epsilon then w.h.p. Gn,pG_{n,p} has a homomorphism from Gn,pG_{n,p} to C2+1C_{2\ell+1} so long as its odd-girth is at least 2+12\ell+1. On the other hand, we show that if c=4c=4 then w.h.p. there is no homomorphism from Gn,pG_{n,p} to C5C_5. Note that in our range of interest, χ(Gn,p)=3\chi(G_{n,p})=3 w.h.p., implying that there is a homomorphism from Gn,pG_{n,p} to C3C_3.

Keywords

Cite

@article{arxiv.1404.4987,
  title  = {Between 2- and 3-colorability},
  author = {Alan Frieze and Wesley Pegden},
  journal= {arXiv preprint arXiv:1404.4987},
  year   = {2014}
}
R2 v1 2026-06-22T03:54:16.571Z