Department of Mathematics Calendar

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The Department of Mathematics is a bustling place full of new ideas. We host several events that occur throughout the year, including seminars, colloquium, conferences, and social events. Our seminars and colloquium are open to the public: all students, faculty, or alumni who are interested are welcome to join us for exciting talks on the leading edge of mathematics research!

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Algebraic Geometry Seminar

Event Type
Department of Mathematics
347 Altgeld Hall
Nov 29, 2022   3:00 pm  
Lena Ji, University of Michigan
Sheldon Katz

Intermediate Jacobian torsors and applications to rationality for conic bundles

Abstract: Clemens–Griffiths introduced the classical intermediate Jacobian obstruction to rationality for complex threefolds in their proof of the irrationality of the cubic threefold. Recently, over non-closed fields, Hassett–Tschinkel and Benoist–Wittenberg refined this obstruction using torsors over the intermediate Jacobian. In this talk, in the setting of conic bundle threefolds, we study this obstruction and its relation to the arithmetic of the ground field. As an application we construct geometrically rational, irrational examples of conic bundles over non-closed fields, where different obstructions witness irrationality. This work is joint with S. Frei, S. Sankar, B. Viray, and I. Vogt.

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