Reduction Numbers and Multiplicities of Multigraded Structures
Reduction Numbers and Multiplicities of Multigraded Structures
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多级结构的约简数和重数
DOI:
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发表时间:
1997
期刊:
影响因子:
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通讯作者:
Zhongming Tang
中科院分区:
文献类型:
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作者:
M. Herrmann;Eero Hyry;J. Ribbe;Zhongming Tang
The aim of this paper is twofold. First we want to relate the Ž . Cohen]Macaulay property of R I , . . . , I to the Cohen]Macaulay propA 1 r Ž . Ž . erty of the ordinary Rees rings R I j s 1, . . . , r . Then we determine A j the multiplicities of multi-Rees and form rings. In particular, we ask when minimal multiplicity occurs. Ž . Ž . For I s ??? s I s I the multi-Rees algebras R I s R I, . . . , I 1 r A r A Ž . behave to some extent like the ordinary Rees algebras R I . In particuA lar, the Cohen]Macaulay property of such multi-Rees algebras can be characterized in terms of conditions on the local cohomology of the form Ž . Ž Ž .. Ž Ž .. ring gr I including the condition a gr I 0, where a gr I denotes A A A Ž . Ž w x. the a-invariant of gr I see HHR 1 . The a-invariant has in certain A Ž . Ž w cases been related to the reduction exponent r I of the ideal I see T2, x. Ž . GH . Moreover, the Cohen]Macaulay property of R I implies that of A Ž . Ž w x. R I for all r ) 1. The converse is not true in general see HHR1 . But A r Ž . in certain applications the assumption R I is Cohen]Macaulay can be A