Stability for the Anti-Ramsey Number of Matchings

TL;DR

This paper investigates the stability properties of the anti-Ramsey number for matchings, establishing conditions under which certain monochromatic subgraphs must exist in edge-colored complete graphs.

Contribution

It provides a stability result for the anti-Ramsey number of matchings, identifying specific monochromatic subgraphs when large rainbow matchings are absent.

Findings

If no rainbow matching of size s+2 exists, the graph contains a large monochromatic complete subgraph or a specific monochromatic join graph.

The result applies to graphs with a number of colors exceeding a certain threshold g(n,s).

The stability theorem characterizes the structure of edge-colored graphs avoiding large rainbow matchings.

Abstract

Let $n, r, s$ be three positive integers such that $n\geq 2s+5$. Let $K_r$ denote the complete graph of order $r$. Given a graph $F$, the anti-Ramsey number $ar(n,F)$ is defined as the minimum number $C$ such that any edge-coloring of $K_n$ with exactly $C$ colors contains a rainbow copy of $F$. Let $H$ be an edge-colored graph on $K_n$ with at least $g(n,s)$ colors, where \[ g(n,s)=\max\left\{ \binom{n}{2} - \binom{n - s + 1}{2} + 5, \binom{2s - 1}{2} + n + 1 \right\}. \] In this paper, we establish a stability type result for the anti-Ramsey number of matchings. Specifically, if $H$ does not have a rainbow matching of size $s+2$, then $H$ contains either a monochromatic complete graph $K_{n-s}$ or a monochromatic $K_{n - 2s - 1} \vee \overline{K_{2s + 1}}$.