On the Rainbow Tur\'an number of paths

Abstract

Let $F$ be a fixed graph. The rainbow Tur\'an number of $F$ is defined as the maximum number of edges in a graph on $n$ vertices that has a proper edge-coloring with no rainbow copy of $F$ (where a rainbow copy of $F$ means a copy of $F$ all of whose edges have different colours). The systematic study of such problems was initiated by Keevash, Mubayi, Sudakov and Verstra\"ete. In this paper, we show that the rainbow Tur\'an number of a path with $k+1$ edges is less than $\left(\frac{9k}{7}+2\right) n$, improving an earlier estimate of Johnston, Palmer and Sarkar.