The generalised rainbow Tur\'an problem for cycles

Given an edge-coloured graph, we say that a subgraph is rainbow if all of its edges have different colours. Let $\mathrm{ex}(n,H,$rainbow-$F)$ denote the maximal number of copies of $H$ that a properly edge-coloured graph on $n$ vertices can contain if it has no rainbow subgraph isomorphic to $F$. We determine the order of magnitude of $\mathrm{ex}(n,C_s,$rainbow-$C_t)$ for all $s,t$ with $s≠3$. In particular, we answer a question of Gerbner, M'esz'aros, Methuku and Palmer by showing that $\mathrm{ex}(n,C_{2k},$rainbow-$C_{2k})$ is $\mathrm{\Theta }(n^{k-1})$ if $k\geq 3$and$\Theta(n^2)$if$k=2$\mathrm{.}Wealsodeterminetheorderofmagnitudeof$\operatorname{ex}(n,P_\ell,$rainbow-$C_{2k})$forall$k,\ell\geq 2$,where$P_\ell$denotesthepathwith$\ell$ edges.