Pluricanonical maps of stable log surfaces

Abstract

Stable surfaces and their log analogues are the type of varieties naturally occuring as boundary points in moduli spaces. We extend classical results of Kodaira and Bombieri to this more general setting: if $(X,\Delta)$ is a stable log surface with reduced boundary (possibly empty) and $I$ is its global index, then $4I(K_X+\Delta)$ is base-point-free and $8I(K_X+\Delta)$ is very ample. These bounds can be improved under further assumptions on the singularities or invariants, for example, $5(K_X+\Delta)$ is very ample if $(X,\Delta)$ has semi-canonical singularities.