Tamagawanumbrsand class numbers of algebraic tori were introduced and studied by T. Ono in the 60s, and were investigated by Katayama,Morishita. R. Sasaki and others. Recently there are progress on computingTamagawanumbers of Complex multiplication (CM) tori, due to its connections with CM abelian varieties, unitary Shimura varieties and counting abelian varieties over finite fields. In these two talks we shall discuss a few results of cohomological groups of some algebraic tori and applications of them to CM tori. This is based on the joint work with Pei-Xin Liang andHsin-Yi Yang.

（II）2021年10月4日 14:00--15:30