Department of Applied Mathematics, Tongji University, Shanghai, 200092, People's Republic of China
Abstract:
The aim of this paper is to improve a theorem of János Kollár by a different method. For a given smooth complex projective threefold of general type, suppose the plurigenus . Kollár proved that the -canonical map is birational. Here we show that either the -canonical map or the -canonical map is birational and that the -canonical map is stably birational onto its image. Suppose . Then the -canonical map is birational for . In particular, is birational whenever and is birational whenever .