Projective varieties admitting an embedding with Gauss map of rank zero

详细信息    查看全文

• 作者：Satoru Fukasawa ; Katsuhisa Furukawa ; Hajime Kaji
• 关键词：Gauss map ; Inseparable ; Minimal free rational curve ; Normal bundle ; Hypersurface
• 刊名：Advances in Mathematics
• 出版年：2010
• 出版时间：20 August 2010
• 年：2010
• 卷：224
• 期：6
• 页码：2645-2661
• 全文大小：221 K

文摘

We introduce an intrinsic property for a projective variety as follows: there exists an embedding into some projective space such that the Gauss map is of rank zero, which we call (GMRZ) for short. It turns out that (GMRZ) imposes strong restrictions on rational curves on projective varieties: In fact, using (GMRZ), we show that, contrary to the characteristic zero case, the existence of free rational curves does not imply that of minimal free rational curves in positive characteristic case. We also focus attention on Segre varieties, Grassmann varieties, and hypersurfaces of low degree. In particular, we give a characterisation of Fermat cubic hypersurfaces in terms of (GMRZ), and show that a general hypersurface of low degree does not satisfy (GMRZ).