Abstract
Among the several types of closures of an idealI that have been defined and studied in the past decades, the integral closureĪ has a central place being one of the earliest and most relevant. Despite this role, it is often a difficult challenge to describe it concretely once the generators ofI are known. Our aim in this note is to show that in a broad class of ideals their radicals play a fundamental role in testing for integral closedness, and in caseI ≠Ī, ✓I is still helpful in finding some fresh new elements inĪ/I. Among the classes of ideals under consideration are: complete intersection ideals of codimension two, generic complete intersection ideals, and generically Gorenstein ideals.
Mathematics Subject Classification (1991)
Primary: 13H10 Secondary: 13D40, 13D45, 13H15Preview
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References
- 1.D. Bayer and M.E. Stillman,Macaulay, A computer algebra system for computing in Algebraic Geometry and Commutative Algebra, 1990. Available via anonymous ftp from zariski.harvard.eduGoogle Scholar
- 2.W. Bruns and J. Herzog,Cohen-Macaulay Rings, Cambridge University Press, Cambridge, 1993MATHGoogle Scholar
- 3.R.-O. Buchweitz, Contributions à la théorie des singularités, Thèse (1981), Université de Paris VIIGoogle Scholar
- 4.A. Corso and C. Polini, Links of prime ideals and their Rees algebras, J. Algebra178, 224–238 (1995)MATHCrossRefMathSciNetGoogle Scholar
- 5.A. Corso and C. Polini, Reduction number of links of irreducible varieties, J. Pure & Applied Algebra121, 29–43 (1997)MATHCrossRefMathSciNetGoogle Scholar
- 6.A. Corso, C. Polini, and W.V. Vasconcelos, Links of prime ideals, Math. Proc. Camb. Phil. Soc.115, 431–436 (1994)MATHMathSciNetGoogle Scholar
- 7.D. Eisenbud,Commutative Algebra with a view toward Algebraic Geometry, Springer-Verlag, Berlin-Heidelberg-New York, 1995MATHGoogle Scholar
- 8.D. Eisenbud, C. Huneke, and W.V. Vasconcelos, Direct methods for primary decomposition, Invent. Math.110, 207–235 (1992)MATHCrossRefMathSciNetGoogle Scholar
- 9.D. Eisenbud and B. Sturmfels, Binomial ideals, Duke Math. J.84, 1–45 (1996)MATHCrossRefMathSciNetGoogle Scholar
- 10.S. Goto, Integral closedness of complete intersection ideals, J. Algebra108, 151–160 (1987)MATHCrossRefMathSciNetGoogle Scholar
- 11.J. Herzog, Ein Cohen-Macaulay Kriterium mit Anwendungen auf den Konormalenmodul und Differentialmodul, Math. Z.163, 149–162 (1978)MATHCrossRefMathSciNetGoogle Scholar
- 12.C. Huneke, The primary components of and integral closures of ideals in 3-dimensional regular local rings, Math. Ann.275, 617–635 (1987)CrossRefMathSciNetGoogle Scholar
- 13.E. Kunz, Almost complete intersections are not Gorenstein rings, J. Algebra28, 111–115 (1974)MATHCrossRefMathSciNetGoogle Scholar
- 14.J. Lipman and B. Teissier, Pseudo-rational local rings and a theorem of Briançon-Skoda, Michigan Math. J.28, 97–116 (1981)MATHCrossRefMathSciNetGoogle Scholar
- 15.S. McAdam,Asymptotic prime divisors, Lecture Notes in Mathematics1023, Springer-Verlag, Berlin-Heidelberg-New York-Tokyo, 1983MATHGoogle Scholar
- 16.H. Matsumura,Commutative Ring Theory, Cambridge University Press, Cambridge, 1986MATHGoogle Scholar
- 17.S. Morey, Equations of blowups of ideals of codimension two and three, J. Pure & Applied Algebra,109, 197–211 (1996)MATHCrossRefMathSciNetGoogle Scholar
- 18.D.G. Northcott and D. Rees, Reductions of ideals in local rings, Proc. Camb. Phil. Soc.50, 145–158 (1954)MATHCrossRefMathSciNetGoogle Scholar
- 19.S. Noh and W.V. Vasconcelos, TheS 2-closure of a Rees algebra, Results in Mathematics23, 149–162 (1993)MATHMathSciNetGoogle Scholar
- 20.C. Polini and B. Ulrich, Linkage and reduction number, Math. Ann. (to appear)Google Scholar
- 21.L.J. Ratliff, Jr., Locally quasi-unmixed Noetherian rings and ideals of the principal class, Pacific J. Math.52, 185–205 (1974)MATHMathSciNetGoogle Scholar
- 22.A. Simis, B. Ulrich, and W.V. Vasconcelos, Cohen-Macaulay Rees algebras and degrees of polynomial relations, Math. Ann.301, 421–444 (1995)MATHCrossRefMathSciNetGoogle Scholar
- 23.W.V. Vasconcelos, Ideals generated by regular sequences, J. Algebra6, 309–316 (1967)MATHCrossRefMathSciNetGoogle Scholar
- 24.W.V. Vasconcelos,Computational Methods in Commutative Algebra and Algebraic Geometry, Algorithms and Computation in Mathematics, Vol. 2, Springer-Verlag, Berlin-Heidelberg-New York, 1998Google Scholar
- 25.O. Zariski and P. Samuel,Commutative Algebra, Vol. II, Van Nostrand, Princeton, 1960MATHGoogle Scholar
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