Rainbow common graphs must be forests
The electronic journal of combinatorics, Tome 32 (2025) no. 3
We study the rainbow version of the graph commonness property: a graph $H$ is $r$-rainbow common if the number of rainbow copies of $H$ (where all edges have distinct colors) in an $r$-coloring of edges of $K_n$ is maximized asymptotically by independently coloring each edge uniformly at random. $H$ is $r$-rainbow uncommon otherwise. We show that if $H$ has a cycle, then it is $r$-rainbow uncommon for every $r$ at least the number of edges of $H$. This generalizes a result of Erdős and Hajnal, and proves a conjecture of De Silva, Si, Tait, Tunçbilek, Yang, and Young.
DOI :
10.37236/12594
Classification :
05C15, 05D10, 05C80, 05D40
Mots-clés : rainbow common, rainbow uncommon, extremal graph theory, probability method
Mots-clés : rainbow common, rainbow uncommon, extremal graph theory, probability method
Affiliations des auteurs :
Yihang Sun  1
@article{10_37236_12594,
author = {Yihang Sun},
title = {Rainbow common graphs must be forests},
journal = {The electronic journal of combinatorics},
year = {2025},
volume = {32},
number = {3},
doi = {10.37236/12594},
zbl = {8097635},
url = {http://geodesic.mathdoc.fr/articles/10.37236/12594/}
}
Yihang Sun. Rainbow common graphs must be forests. The electronic journal of combinatorics, Tome 32 (2025) no. 3. doi: 10.37236/12594
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