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Distribution of colors in Gallai colorings

Authors :
Gyárfás, András
Pálvölgyi, Dömötör
Patkós, Balázs
Wales, Matthew
Source :
European Journal of Combinatorics, 86 (2020) 103087
Publication Year :
2019

Abstract

A Gallai coloring is an edge coloring that avoids triangles colored with three different colors. Given integers $e_1\ge e_2 \ge \dots \ge e_k$ with $\sum_{i=1}^ke_i={n \choose 2}$ for some $n$, does there exist a Gallai $k$-coloring of $K_n$ with $e_i$ edges in color $i$? In this paper, we give several sufficient conditions and one necessary condition to guarantee a positive answer to the above question. In particular, we prove the existence of a Gallai-coloring if $e_1-e_k\le 1$ and $k \le \lfloor n/2\rfloor$. We prove that for any integer $k\ge 3$ there is a (unique) integer $g(k)$ with the following property: there exists a Gallai $k$-coloring of $K_n$ with $e_i$ edges in color $i$ for every $e_1\le\dots \le e_k$ satisfying $\sum_{i=1}^ke_i={n\choose 2}$, if and only if $n\ge g(k)$. We show that $g(3)=5$, $g(4)=8$, and $2k-2\le g(k)\le 8k^2+1$ for every $k\ge 3$.

Subjects

Subjects :
Mathematics - Combinatorics

Details

Database :
arXiv
Journal :
European Journal of Combinatorics, 86 (2020) 103087
Publication Type :
Report
Accession number :
edsarx.1903.04380
Document Type :
Working Paper
Full Text :
https://doi.org/10.1016/j.ejc.2020.103087