Model theory of differential fields with finite group actions

Abstract

Let G be a finite group. We explore the model theoretic properties of the class of differential fields of characteristic zero in m commuting derivations equipped with a G-action by differential field automorphisms. In the language of G-differential rings (i.e. the language of rings with added symbols for derivations and automorphisms), we prove that this class has a modelcompanion – denoted G -DCF0,m. We then deploy the model-theoretic tools developed in the first author’s paper [11] to show that any model of G -DCF0,m is supersimple (but unstable whenG is nontrivial), a PAC-differential field (and hence differentially large in the sense of the second author and Tressl [30]), and admits elimination of imaginaries after adding a tuple of parameters. We also address model-completeness and supersimplicity of theories of bounded PACdifferential fields (extending the results of Chatzidakis-Pillay [5] on bounded PAC-fields).