Bounded morphisms

Abstract

A bounded automorphism of a field or a group with trivial approximate centre is definable. In an expansion of a field by a Pfaffian family F of additive endomorphisms such that algebraic closure in the expansion coincides with relative field-algebraic closure of the F-substructure generated, a bounded endomorphism, possibly composed with a power of the Frobenius, is a composition of endomorphisms associated with F.