Matthias Mnich (Eindhoven): Minimal feedback vertex sets in tournaments

A tournament T is an orientation of a complete graph. A feedback vertex set F for T contains some vertex from every vertex-induced directed cycle of T. Let M(n) denote the maximum number of minimal feedback vertex sets over all tournaments on $n$ vertices, and let beta be the smallest number such that beta^n >= M(n) for all n. Moon (1971) proved that 1.4757 <= beta <= 1.717, here we prove beta=21^(1/7), which is approximately 1.54486.