Algebra Seminar

Speaker: Haowen Zhang (Jussieu University )

"Weak approximation for homogeneous spaces over C((X,Y)) or C((X))(Y)"

Time: 14:30

Room: ZOOM

We study obstructions to weak approximation for connected linear groups and homogeneous spaces with connected or abelian stabilizers over finite extensions of C((X,Y)) or functions fields of curves over C((X)). We show that for connected linear groups, the usual Brauer-Manin obstruction works as in the case of tori, using some dévissage argument. However, this Brauer-Manin obstruction is not enough for homogeneous spaces, and we should somehow combine the Brauer-Manin obstruction with the descent obstruction using torsors under quasi-trivial tori, another natural tool used in the study of such questions, as done by Izquierdo and Lucchini Arteche for the study of obstruction to rational points.