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On some properties of partial intersection schemes.

Alfio Ragusa, Giuseppe Zappalà (2003)

Collectanea Mathematica

Partial intersection subschemes of Pr of codimension c were used to furnish various graded Betti numbers which agree with a fixed Hilbert function. Here we study some further properties of such schemes; in particular, we show that they are not in general licci and we give a large class of them which are licci. Moreover, we show that all partial intersections are glicci. We also show that for partial intersections the first and the last Betti numbers, say m and p respectively, give bounds each other;...

On the endomorphism ring and Cohen-Macaulayness of local cohomology defined by a pair of ideals

Thiago H. Freitas, Victor H. Jorge Pérez (2019)

Czechoslovak Mathematical Journal

Let 𝔞 , I , J be ideals of a Noetherian local ring ( R , 𝔪 , k ) . Let M and N be finitely generated R -modules. We give a generalized version of the Duality Theorem for Cohen-Macaulay rings using local cohomology defined by a pair of ideals. We study the behavior of the endomorphism rings of H I , J t ( M ) and D ( H I , J t ( M ) ) , where t is the smallest integer such that the local cohomology with respect to a pair of ideals is nonzero and D ( - ) : = Hom R ( - , E R ( k ) ) is the Matlis dual functor. We show that if R is a d -dimensional complete Cohen-Macaulay ring and H I , J i ( R ) = 0 ...

On the free character of the first Koszul homology module.

Antonio García Rodicio (1991)

Extracta Mathematicae

Let (A,M,K) denote a local noetherian ring A with maximal ideal M and residue field K. Let I be an ideal of A and E the Koszul complex generated over A by a system of generators of I.The condition: H1(E) is a free A/I-module, appears in several important results of Commutative Algebra. For instance:- (Gulliksen [3, Proposition 1.4.9]): The ideal I is generated by a regular sequence if and only if I has finite projective dimension and H1(E) is a free A/I-module.- (André [2]): Assume that A is a complete...

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