On Pseudo-Effectivity and Volumes of Adjoint Classes in Kähler Families with Projective Central Fiber

Abstract

This paper is devoted to studying the deformation behavior of pseudo-effective canonical divisors and volumes of adjoint classes in Kähler families. Based on recent developments in the Kähler minimal model program, for flat families with fiberwise canonical singularities, we establish the global stability of the pseudo-effectivity of canonical divisors and uniruledness, assuming in addition that one fiber is projective, while the same conclusion for Kähler threefolds is also true without the projectivity assumption of the central fiber. For a smooth Kähler family whose central fiber is projective with a big adjoint class, we show that its volume remains locally constant. Finally, using the (relative) minimal model program for Kähler threefolds, we verify the deformation invariance of volumes of adjoint classes and plurigenera for smooth families of Kähler threefolds, thereby confirming Siu's invariance of plurigenera conjecture in dimension three.

V2: Minor revision. The statement and proof of some lemmas (Proposition 2.26) have been revised. The statements of the main theorems are mostly unaffected. The proof of Corollary 1.3 has been revised. 45 pages. All comments and remarks are welcome