SFU NT + AG Seminar: Lena Ji

Clemens–Griffiths introduced the classical intermediate Jacobian obstruction to rationality for complex threefolds, and used it to show 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, we identify these intermediate Jacobian torsors for conic bundle threefolds, and we give applications to rationality over non-closed fields. This talk is based on joint work with S. Frei, S. Sankar, B. Viray, and I. Vogt, and on joint work with M. Ji.