Etale difference algebraic groups
Also appears in collection : Model Theory, Difference/Differential Equations and Applications / Théorie des modèles, équations différentielles et aux différences et applications
Difference algebraic groups, i.e, groups defined by algebraic difference equations occur naturally as the Galois groups of linear differential or difference equations depending on a discrete parameter. If the linear equation has a full set of algebraic solutions, the corresponding Galois group is an étale difference algebraic group. Like étale algebraic groups can be described as finite groups with a continuous action of the absolute Galois group of the base field, étale difference algebraic groups can be described as certain profinite groups with some extra structure. I will present a decomposition theorem for étale difference algebraic groups, which shows that any étale difference algebraic group can be build from étale algebraic groups and finite groups equipped with an endomorphism.
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