Proof. [04UZ]
Original official author HTML, exact retained edition. Historical TeX conversion verdicts remain unchanged. Cited-edition alignment and mathematical self-containment are not assessed.
Complete original source context ยท Original author HTML
Proof.
(1) The condition that is semi-ample over is obviously necessary, since for every -model of , the divisor is -linearly equivalent to the restriction of to . Conversely, assume that is semi-ample over , and let be a proper -model of . Then applying [HX13, 2.12] to the -pair , we see that has a good minimal -model. Condition (1) of [HX13, 2.12] follows from our assumption, and condition (2) follows from the following observation. Let be a positive integer such that is Cartier. Over a sufficiently small open neighbourhood of in , we have an isomorphism of -algebras
where with the structural morphism. Thus it suffices to show that
is a finitely generated -algebra. If we denote by the maximum of the multiplicities of the components in then we may assume that , so that
is a pair. Hence, the finite generation of follows from [BCHM10].