MATH Seminar

Title: More examples of non-rational adjoint groups
Seminar: Algebra
Speaker: Nivedita Bhaskhar of Emory University
Contact: David Zureick-Brown, dzb@mathcs.emory.edu
Date: 2014-01-21 at 4:00PM
Venue: W302
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Abstract:
A k-variety is said to be rational if its function field is purely transcendental over k. The first example of a non-rational adjoint k-group PSO(q) was given by Merkurjev as a consequence of his computations of R-equivalence classes of adjoint classical groups. The quadratic form in question has non-trivial discriminant which property is used crucially in the proof. Gille provided the first example of a quadratic form of trivial discriminant whose associated adjoint group is non-rational. In this talk we give a recursive construction to produce examples of $k_n$-quadratic forms $q_n$ in the n-th power of the fundamental ideal in the Witt ring whose corresponding adjoint groups PSO($q_n$) are not (stably) rational.

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