2018 年 72 巻 2 号 p. 269-275
We define the geometric simpleness for toroidal groups. We give an example of quasi-abelian variety which is geometrically simple, but not simple. We show that any quasi-abelian variety is isogenous to a product of geometrically simple quasi-abelian varieties. We also show that the Q-extension of the ring of all endomorphisms of a geometrically simple quasi-abelian variety is a division algebra over Q.