Nielsen realization problem for derived automorphisms of generic K3 surfaces

TL;DR

This paper investigates the structure of finite subgroups of derived automorphisms of generic K3 surfaces, revealing their orders, conjugacy classes, and connections to cubic fourfolds, using Bridgeland stability conditions.

Contribution

It characterizes the finite subgroups of derived automorphisms of generic K3 surfaces and links automorphism orders to geometric structures like cubic fourfolds.

Findings

Finite subgroups have order two or are finite up to shifts.

A K3 surface admits a cubic fourfold if it has a derived automorphism of order three.

Subgroups fix Bridgeland stability conditions up to complex actions.

Abstract

We prove that all nontrivial finite subgroups of derived automorphisms of K3 surfaces of Picard number one have order two and give formulas for the numbers of their conjugacy classes. We also obtain a similar result for the subgroups which are finite up to shifts. This in turn shows that such a K3 surface admits an associated cubic fourfold if and only if it has a derived automorphism of order three up to shifts. These results are achieved by proving that such a subgroup fixes a Bridgeland stability condition up to $\mathbb{C}$-actions. We also establish similar existence results for curves, twisted abelian surfaces, generic twisted K3 surfaces, and standard autoequivalences on surfaces.