MTGFOP · Model theory and geometry of fields with operators

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Project objective

We will consider a field K with an operator of one of the following 4 kinds: derivation, automorphism, Hasse derivation and derivation of Frobenius. We are interested in results of two kinds -- geometric and model theoretical (i.e. concerning first-order properties of those structures).First, I explain what kind of geometric results we expect. For an algebraic variety X (or scheme) over K, we enrich the geometry of X by extending the operator to the structure sheaf of X. In the case of a derivation such an enriched geometric structure is called (Buium) a D-variety. We want to extend Buium's results about D-varieties (as description of D-groups or isotriviality of projective D-varieties) into a wider class of geometric objects where the operator is one of the remaining 3 kinds.The results already obtained (by Buium for derivations and by Anand Pillay and me for automorphisms) yield diophantine consequences in the style of the Mordell-Lang conjecture. We hope that an analysis of the remaining cases yields similar consequences. From the logical standpoint, we will study the first-order properties of the above geometric structures. We are interested in quantifier elimination results, i.e. in deciding the combinatorial complexity of the definable sets there.Another goal is to study the first order properties of the field with an operator itself. There is a great deal of work already done in the cases of derivations, automorphism and Hasse derivations but the case of derivations of Frobenius was only treated b y me in one paper. So, we want to continue working on model theory of fields with derivations of Frobenius (e.g. work out the theory of definable groups there).The last thing to be done is studying the limit theory of derivation of Frobenius when the power of Frobenius map grows to infinity (i.e. we get the theory of derivation of nonstandard Frobenius). We would like to prove that this theory is related to e.c. fields with a derivation of an endomorphism.

Original text from CORDIS.

Participants

• UNIVERSITé PARIS 7 DENIS DIDEROT · PARISCoordinatorCity levelFrance

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