Generalized rainbow Turán numbers of odd cycles

Abstract

Given graphs $F$ and $H$, the generalized rainbow Turán number $\text{ex}(n,F,\text{rainbow-}H)$ is the maximum number of copies of $F$ in an $n$-vertex graph with a proper edge-coloring that contains no rainbow copy of $H$. B. Janzer determined the order of magnitude of $\text{ex}(n,C_s,\text{rainbow-}{C}_t)$ for all $s\ge 4$ and $t\ge 3$, and a recent result of O. Janzer implied that $\text{ex}(n,C_3,\text{rainbow-}{C}_{2k})=O(n^{1+1/k})$. We prove the corresponding upper bound for the remaining cases, showing that $\text{ex}(n,C_3,\text{rainbow-}{C}_{2k+1})=O(n^{1+1/k})$. This matches the known lower bound for $k$ even and is conjectured to be tight for $k$ odd.