English

Homomorphism thresholds for odd cycles

Combinatorics 2020-05-26 v2

Abstract

The interplay of minimum degree conditions and structural properties of large graphs with forbidden subgraphs is a central topic in extremal graph theory. For a given graph FF we define the homomorphism threshold as the infimum over all α[0,1]\alpha\in[0,1] such that every nn-vertex FF-free graph GG with minimum degree at least αn\alpha n has a homomorphic image HH of bounded order (independent of nn), which is FF-free as well. Without the restriction of HH being FF-free we recover the definition of the chromatic threshold, which was determined for every graph FF by Allen et al. [Adv. Math. 235 (2013), 261-295]. The homomorphism threshold is less understood and we address the problem for odd cycles.

Keywords

Cite

@article{arxiv.1712.07026,
  title  = {Homomorphism thresholds for odd cycles},
  author = {Oliver Ebsen and Mathias Schacht},
  journal= {arXiv preprint arXiv:1712.07026},
  year   = {2020}
}

Comments

21 pages, second version addresses changes arising from the referee reports

R2 v1 2026-06-22T23:23:16.010Z