Finiteness properties of affine difference algebraic groups

We establish several finiteness properties of groups defined by algebraic difference equations. One of our main results is that a subgroup of the general linear group defined by possibly infinitely many algebraic difference equations in the matrix entries can indeed be defined by finitely many such equations. As an application, we show that the difference ideal of all difference algebraic relations among the solutions of a linear differential equation is finitely generated.
38 pages. This version (v2) is a major reorganization of the first version (v1). Roughly, the first four sections of v2 correspond to the first four sections of v1. The 5th section of v2 corresponds to the 6th section of v1 and the 6th section of v2 corresponds to the 9th section of v1. The 7th section of v2 is new. The sections of v1 not contained in v2 will appear elsewhere