On the anti-Ramsey threshold

TL;DR

This paper determines the threshold for when a random graph almost surely guarantees a rainbow copy of a dense fixed graph under any proper edge-colouring, using advanced graph decomposition techniques.

Contribution

It establishes the anti-Ramsey threshold for dense graphs in random graphs and introduces a novel graph decomposition lemma.

Findings

Identifies the anti-Ramsey threshold for dense graphs in random graphs.

Introduces a new graph decomposition lemma of independent interest.

Provides a probabilistic threshold result for rainbow subgraphs.

Abstract

We say that a graph $G$ is anti-Ramsey for a graph $H$ if any proper edge-colouring of $G$ yields a rainbow copy of $H$, i.e. a copy of $H$ whose edges all receive different colours. In this work we determine the threshold at which the binomial random graph becomes anti-Ramsey for any fixed graph $H$, given that $H$ is sufficiently dense. Our proof employs a graph decomposition lemma in the style of the Nine Dragon Tree theorem that may be of independent interest.