Effective bounds for the number of MMP-series of a smooth threefold

Abstract

We prove that the number of MMP-series of a smooth projective threefold of positive Kodaira dimension and of Picard number equal to three is at most two.

10 pages. Accepted for publication in the Glasgow Mathematical Journal. Theorem 1.1 in the previous version has been removed because the proof contained an error. The bound in Theorem 1.2 has been improved