Enriques surfaces with finite automorphism group in positive characteristic

Abstract

We classify Enriques surfaces with smooth K3 cover and finite automorphism group in arbitrary positive characteristic. The classification is the same as over the complex numbers except that some types are missing in small characteristics. Moreover, we give a complete description of the moduli of these surfaces. Finally, we realize all types of Enriques surfaces with finite automorphism group over the prime fields ${\mathbb{F}}_p$ and $\mathbb{Q}$ whenever they exist.

arXiv comment71 pages, comments welcome v2: corrected some minor mistakes, added application to semi-symplectic automorphisms