On the Gorenstein property of the associated graded ring of a power of an ideal

It has been proved by Herrmann, Ribbe and Schenzel that in a local ring the Gorensteiness of the associated graded ring of a power of an ideal implies the Gorensteiness of the associated graded ring of the ideal provided it is Cohen-Macaulay and the height of the ideal is at least two. We give a new proof to this theorem which covers also the height one case and so answer to a question of Herrmann, Ribbe and Schenzel whether their result holds for ideals of height one.     

On the depth of certain graded rings associated to an ideal

Let (R,m) be a local ring and Ian ideal of R. In this work we find conditions on Ithat allow us to describe simple relations among depth R(It), depth gr_I(R), depth S(I) and depth S(I/I ²). These relations are useful also from a practical point, of view since it is usually difficult to evaluate depth gr_I(R) and depth S(I/I ²) even with the help of a computer. Furthermore we study the class of ideals that satisfy one of the required conditions and we show that ideals generated by quadratic sequences are in this class     

On the depth of the canonical modules of graded rings associated to an ideal

In this article, we first give a necessary and sufficient condition on a finite purely nonabelian p-group G for the group Aut _c (G) of central automorphisms of G to be elementary Abelian. We then generalize our result to the homocyclic case.     

Duplication of a module along an ideal

Let A be a commutative ring and I an ideal of A. The amalgamated duplication of A along I, denoted by \({A \bowtie I}\) , is the special subring of \({A \times A}\) defined by \({A \bowtie I } := \pi \times_{\frac{A}{I}} \pi = \{(a, a + i) \mid a \in A, i \in I\}\) . We are interested in some basic and homological properties of a special kind of \({A \bowtie I}\) -modules, called the duplication of M along I with M is an A-module, and defined by \({M \bowtie I := \{(m, m') \in M \times M \mid m - m^{\prime} \in IM\}}\) . The new results generalize some results on amalgamated duplication of a ring along an ideal.     

Orbits of the automorphism group of a module over a principal ideal ring.

Orbits of the automorphism group of a finitely generated module over a principal ideal ring are described in terms of canonical representatives and by a complete system of invariants. For a primary module, a natural bijection to a sum of two Young diagrams is established for the set of orbits and the set of partitions of the Young diagram corresponding to the module, which allows us to calculate the number of orbits.     

The f-depth of an ideal on a module

Let be an ideal of a Noetherian local ring and a finitely generated -module. The f-depth of on is the least integer such that the local cohomology module is not Artinian. This paper presents some part of the theory of f-depth including characterizations of f-depth and a relation between f-depth and f-modules.

     

The Castelnuovo regularity of the Rees algebra and the associated graded ring

It is shown that there is a close relationship between the invariants characterizing the homogeneous vanishing of the local cohomology and the Koszul homology of the Rees algebra and the associated graded ring of an ideal. From this it follows that these graded rings share the same Castelnuovo regularity and the same relation type. The main result of this paper is however a simple characterization of the Castenuovo regularity of these graded rings in terms of any reduction of the ideal. This characterization brings new insights into the theory of -sequences.

     

A companion ideal of a multiplication module

Let M _R be a faithful multiplication module, where R is a commutative ring. As defined by Anderson, this ideal has proved to be useful in studying multiplication modules. First of all a cancellation law involving M and the ideals contained in is proved. Among various applications given, the following result is proved:: There exists a canonical isomorphism from onto such that for any ( Hom _R(M,M), x ( M, a ( (M), (xa) = x.(()(a). As an application of this later result it is proved that M is quasi-injective if and only if (M) is quasi-injective.     

Artinian ring and amalgamated algebra along an ideal

Let R and S be two commutative rings with unity, let I be an ideal of S and $$varphi : R longrightarrow S$$ be a ring homomorphism. In this paper, we give a characterization for the the amalgamated algebra $$R bowtie ^varphi I$$ to be an Artinian ring.     

When the dual of an ideal is a ring

Let R be a commutative integral domain with identity with quotient field K, and let I be a nonzero ideal of R. We analyze several general and particular instances when I^–1 is a subring of K. We then apply some of our results to show that certain non-maximal prime ideals in Prüfer domains are divisorial.     

环的次极大理想

引入了环的次极大理想的概念，讨论了它的性质，并得到比环的理想的准素分解定理更普遍的结论。     

A strongly graded ring that is

We construct a ring that is strongly graded by the integers such that it is not graded equivalent to a skew group ring. This is in contrast to the finite case and the results of Cohen and Montgomery, in which every strongly graded ring is graded equivalent to a skew group ring ^{2 2}1991 mathematics subject classification: 16D90, 16S35, 16S40, 16S50, 16W50      

Normal basis for an ideal in a local ring

An effective construction is given for a normal ideal basis (when it exists) in local number field extensions with higher ramification.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 64, pp. 64–68, 1976.