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Proceedings of the American Mathematical Society
ISSN 1088-6826 (e) ISSN 0002-9939 (p)
     

Consecutive cancellations in Betti numbers of local rings

Author(s): Maria Evelina Rossi; Leila Sharifan
Journal: Proc. Amer. Math. Soc. 138 (2010), 61-73.
MSC (2000): Primary 13D02
Posted: August 28, 2009
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Abstract: Let $ I$ be a homogeneous ideal in a polynomial ring $ P$ over a field. By Macaulay's Theorem there exists a lexicographic ideal $ L=\operatorname{Lex}(I)$ with the same Hilbert function as $ I. $ Peeva has proved that the Betti numbers of $ P/I $ can be obtained from the graded Betti numbers of $ P/L$ by a suitable sequence of consecutive cancellations. We extend this result to any ideal $ I$ in a regular local ring $ (R,\mathfrak{n}) $ by passing through the associated graded ring. To this purpose it will be necessary to enlarge the list of the allowed cancellations. Taking advantage of Eliahou-Kervaire's construction, we present several applications. This connection between the graded perspective and the local one is a new viewpoint, and we hope it will be useful for studying the numerical invariants of classes of local rings.


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Additional Information:

Maria Evelina Rossi
Affiliation: Department of Mathematics, University of Genoa, Via Dodecaneso 35, 16146 Genoa, Italy
Email: rossim@dima.unige.it

Leila Sharifan
Affiliation: Faculty of Mathematics and Computer Science, Amirkabir University of Technology, 424, Hafez Avenue, 15914 Tehran, Iran
Email: leila-sharifan@aut.ac.ir

DOI: 10.1090/S0002-9939-09-10010-2
PII: S 0002-9939(09)10010-2
Keywords: Minimal free resolution, filtered module, associated graded module, Betti numbers, lexicographic ideal, standard bases.
Received by editor(s): February 11, 2009,
Received by editor(s) in revised form: April 17, 2009
Posted: August 28, 2009
Communicated by: Bernd Ulrich
Copyright of article: Copyright 2009, American Mathematical Society
The copyright for this article reverts to public domain after 28 years from publication.


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