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Seminar

DDC - Model Theory Seminar: Sets, groups, and fields definable in vector spaces with a bilinear form October 26, 2020 (08:00 AM PDT - 09:00 AM PDT)
Parent Program:
Location: MSRI: Online/Virtual
Speaker(s) Jan Dobrowolski (University of Wrocław)
Description

To participate in this seminar, please register here: https://www.msri.org/seminars/25206

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Abstract/Media

To participate in this seminar, please register here: https://www.msri.org/seminars/25206

Abstract:

There is a long history of study of algebraic objects definable in classical mathematical structures.

As a prominent example, by results of Weil, Hrushovski, and van den Dries, it is known that the groups definable in an algebraically closed field K are precisely the algebraic groups over K, and the only infinite field definable in K is the field K itself. 

The talk will be a report on my recent work on dimension, definable groups, and definable fields in vector spaces over algebraically closed [real closed] fields equipped with a non-degenerate alternating bilinear form or a non-degenerate [positive-definite] symmetric bilinear form. The main result states that every definable group is (algebraic-by-abelian) by-algebraic [(semialgebraic-by-abelian)-by-semialgebraic], which, in particular, answers a question of Granger. It follows that every definable field is definable in the field of scalars, hence either finite or definably isomorphic to it [finite or algebraically closed or real closed].

If time permits, I will very briefly discuss some model theoretic phenomena in the considered structures.

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