Hoàng-Reed conjecture holds for tournaments
Résumé
Hoàng-Reed conjecture asserts that every digraph $D$ has a collection $\cal C$ of circuits $C_1,\dots,C_{\delta ^+}$, where $\delta ^+$ is the minimum outdegree of $D$, such that the circuits of $\cal C$ have a forest-like structure. Formally, $|V(C_i)\cap (V(C_1)\cup \dots \cup V(C_{i-1}))|\leq 1$, for all $i=2,\dots ,\delta^+$. We verify this conjecture for the class of tournaments.