Cyclic covers of normal graded rings

Cyclic covers of normal graded rings
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普通分级环的循环盖

DOI:
10.2996/kmj/1106168814
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发表时间:
2001
影响因子:
0.6
通讯作者:
Kei
Kei
中科院分区:
数学4区
文献类型:
--
作者:
M. Tomari;Kei

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利用正规分次环R,R,X;D的Pinkham-Demazure刻划,给出了正规分次环的分次循环覆盖的刻画。利用循环覆盖的几何刻画,证明了循环覆盖S具有Pinkham-Demazure刻划S GR~Y;~D[定理1.3],由此得到了R在O2中的指标1覆盖[推论1.7]的刻画,作为这种刻画的应用,我们给出了正规分次奇点是Kawamata对数终端或对数正则的判据.此外,在O_3中,我们研究了Kummer型循环覆盖与利用Verones子环得到的循环覆盖之间的关系。我们的结果推广了S.Mori关于分次阶乘整环的结构定理。
We give a description of a graded cyclic cover of a normal graded ring in terms of the Pinkham-Demazure description of normal graded rings R ˆ R…X ;D†. With the geometric description of Cl…R†, it is shown that our cyclic cover S possesses the Pinkham-Demazure description S GR…Y ; ~ D† [Theorem 1.3], by which we obtain a description of an index one cover [Corollary 1.7] of R. In O2, as an application of this description, we give criteria for the normal graded singularities to be Kawamata log terminal or to be log canonical. Further, in O3 we study the relations between cyclic covers of the Kummer type and cyclic covers obtained by using Veronese subrings. Our results extend S. Mori's structure theorem regarding graded factorial domains.
Tomari,M.:“特殊类型的高维纯椭圆奇点的规范过滤”Invent.Math。
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