English

Monochromatic components with many edges in random graphs

Combinatorics 2026-02-18 v2

Abstract

In an rr-coloring of edges of the complete graph on nn vertices, how many edges are there in the largest monochromatic connected component? A construction of Gy\'arf\'as shows that for infinitely many values of rr, there exist colorings where all monochromatic components have at most (1r2r+o(1))(n2)\left(\frac{1}{r^2-r}+o(1)\right)\binom{n}{2} edges. Conlon, Luo, and Tyomkyn conjectured that components with at least this many edges are attainable for all r3r \ge 3. This was proven by Luo for r=3r=3, along with a lower bound of 1r2r+54(n2)\frac{1}{r^2-r+\frac54}{n\choose 2} for all r2r\ge 2, and by Conlon, Luo, and Tyomkyn for r=4r=4. In this paper, we look at extensions of this problem where the graph being rr-colored is a sparse random graph or a graph of high minimum degree. By extending several intermediate technical results from previous work in the complete graph setting, we prove analogues of the bound for general rr in both the sparse random setting and the high minimum degree setting, as well as the bound for r=3r=3 in the latter setting.

Keywords

Cite

@article{arxiv.2509.01766,
  title  = {Monochromatic components with many edges in random graphs},
  author = {Hannah Fox and Sammy Luo},
  journal= {arXiv preprint arXiv:2509.01766},
  year   = {2026}
}

Comments

15 pages, comments welcome. Edited to correct attribution error in abstract

R2 v1 2026-07-01T05:16:13.362Z