On the computation of Ratliff-Rush closure

Powers of monomial ideals and the Ratliff-Rush operation

Powers of (monomial) ideals is a subject that still calls attraction in various ways. In this paper we present a nice presentation of high powers of ideals in a certain class in $\mathbb K[x_1, \ldots, x_n]$ and $\mathbb K[[x_1, \ldots, x_n]]$. As an interesting application it leads to an algorithm for computation of the Ratliff--Rush operation on ideals in that class. The Ratliff--Rush operation itself has several applications, for instance, if $I$ is a regular $\mathfrak m$-primary ideal in a local ring $(R,m)$, then the Ratliff--Rush associated ideal $\tilde I$ is the unique largest ideal c…

Ratliff-Rush Filtration, Regularity and depth of Higher Associated graded modules: Part I

In this paper we introduce a new technique to study associated graded modules. Let $(A,\m)$ be a Noetherian local ring with $\depth A \geq 2$. Our techniques gives a necessary and sufficient condition for $\depth G_{\m^n}(A) \geq 2$ for all $n \gg 0$. Other applications are also included; most notable is an upper bound regarding the Ratliff-Rush filtration.

Results on the Ratliff-Rush Closure and the Integral Closedness of Powers of Certain Monomial Curves

Starting from \cite{Ayy2} we compute the Groebner basis for the defining ideal, P, of the monomial curves that correspond to arithmetic sequences, and then give an elegant description of the generators of powers of the initial ideal of P, inP. The first result of this paper introduces a procedure for generating infinite families of Ratliff-Rush ideals, in polynomial rings with multivariables, from a Ratliff-Rush ideal in polynomial rings with two variables. The second result is to prove that all powers of inP are Ratliff-Rush. The proof is through applying the first result of this paper combin…

Ratliff-Rush ideal and reduction numbers

Let $(R,m)$ be a Cohen-Macaulay local ring of positive dimension $d$ and infinite residue field. Let $I$ be an m-primary ideal and $J$ a minimal reduction of $I$. In this paper, we show that $\widetilde{r_J(I)}\leq r_J(I)$. This answer to a question that made by M.E. Rossi and I. Swanson in [\ref{Rs}, Question 4.6].

关于一维环中理想的Ratliff-Rush闭包

On the Ratliff-Rush closure of an ideal of a one-dimensional ring

本文在一维Noetherian环中研究理想的渐近Ratliff-Rush数，通过其与约化数的关系，寻找决定该数取得极值的条件。

Ratliff-Rush Filtration, regularity and depth of Higher Associated graded modules: Part II

Let $(A,\m)$ be a Noetherian local ring, let $M$ be a finitely generated \CM $A$-module of dimension $r \geq 2$ and let $I$ be an ideal of definition for $M$. Set $L^I(M) = \bigoplus_{n\geq 0}M/I^{n+1}M$. In part one of this paper we showed that $L^I(M)$ is a module over $\R$, the Rees algebra of $I$ and we gave many applications of $L^I(M)$ to study the associated graded module, $G_I(M)$. In this paper we give many further applications of our technique; most notable is a reformulation of a classical result due to Narita in terms of the Ratliff-Rush filtration. This reformulation can be extend…

Ratliff-Rush closures and linear growth of primary decompositions of ideals

Let $R$ be a commutative Noetherian ring, $E$ a non-zero finitely generated $R$-module and $I$ an ideal of $R$. One purpose of this paper is to show that the sequences $\Ass_RE/ \widetilde{I_E^n}$ and $\Ass_R\widetilde{I^n _E}/\widetilde{I^{n+1}_E}$, $n = 1,2, \dots$, of associated prime ideals are increasing and eventually stabilize. This extends the main result of Mirbagheri and Ratliff \cite[Theorem 3.1]{MR}. In addition, a characterization concerning the set $\widetilde{A^*}(I,E)$ is included. A second purpose of this paper is to prove that $I$ has linear growth primary decompositions for …

Castelnuovo-Mumford regularity and Ratliff-Rush closure

We establish strong relationships between the Castelnuovo-Mumford regularity and the Ratliff-Rush closure of an ideal. Our results have several interesting consequences on the computation of the Ratliff-Rush closure, the stability of the Ratliff-Rush filtration, the invariance of the reduction number, and the computation of the Castelnuovo-Mumford regularity of the Rees algebra and the fiber ring. In particular, we prove that the Castelnuovo-Mumford regularity of the Rees algebra and of the fiber ring are equal for large classes of monomial ideals in two variables, thereby verifying a conjectu…

On the computation of the Ratliff-Rush closure, associated graded ring and invariance of a length

Let $(R,\fm)$ be a Cohen-Macaulay local ring of positive dimension $d$ and infinite residue field. Let $I$ be an $\fm$-primary ideal of $R$ and $J$ be a minimal reduction of $I$. In this paper we show that if $\widetilde{I^k}=I^k$ and $J\cap I^n=JI^{n-1}$ for all $n\geq k+2$, then $\widetilde{I^n}=I^n$ for all $n\geq k$. As a consequence, we can deduce that if $r_J(I)=2$, then $\widetilde{I}=I$ if and only if $\widetilde{I^n}=I^n$ for all $n\geq 1$. Moreover, we recover some main results [\ref{Cpv}] and [\ref{G}]. Finally, we give a counter example for question 3 of [\ref{P1}].

Ratliff-Rush Filtrations associated with ideals and modules over a Noetherian ring

Let $R$ be a commutative Noetherian ring, $M$ a finitely generated $R$-module and $I$ a proper ideal of $R$. In this paper we introduce and analyze some properties of $r(I, M)=\bigcup_{k\geqslant 1} (I^{k+1}M: I^kM)$, {\it the Ratliff-Rush ideal associated with $I$ and $M$}. When $M= R$ (or more generally when $M$ is projective) then $r(I, M)= \widetilde{I}$, the usual Ratliff-Rush ideal associated with $I$. If $I$ is a regular ideal and $\ann M=0$ we show that $\{r(I^n,M) \}_{n\geqslant 0}$ is a stable $I$-filtration. If $M_{\p}$ is free for all ${\p}\in \spec R\setminus \mspec R,$ then under…

Ratliff-Rush 滤链、Hilbert 系数与整闭理想的约化数

Ratliff-Rush filtration, Hilbert coefficients and the reduction number of integrally closed ideals

本文在 Cohen-Macaulay 局部环中建立了整闭理想第三 Hilbert 系数的界，利用边界情形刻画了 Ratliff-Rush 滤链性质，并在特定深度条件下证明了约化数满足 Rossi 的界。

关于Ratliff-Rush过滤、理想reduction数和postulation数的注记

A note on Ratliff-Rush filtration, reduction number and postulation number of $\mathfrak m$-primary ideals

研究了Cohen-Macaulay局部环中m-primary理想的相关性质，证明了在不同维数下，reduction数与postulation数的关系，并推广了Marley关于Hilbert-Samuel函数与多项式关系的结果。

关于Ratliff-Rush指数和Castelnuovo-Mumford正则度的界

Bounds on the Ratliff-Rush Index and the Castelnuovo-Mumford Regularity

本文基于Hilbert系数和减少数，建立了理想Ratliff-Rush指数的上界，并推导了关联graded环的Castelnuovo-Mumford正则度的界，特别研究了二维Buchsbaum环中的情况。

准希尔伯特环与拉蒂夫-拉什滤尘

Quasi-Hilbert rings and Ratliff-Rush filtrations

本文研究了准希尔伯特环的性质，引入了准希尔伯特环的概念，并探讨了其在理想闭包和环完成中的应用。

Ideal containment vs. powers

Let $R$ be a commutative ring with identity. In this note, we study the property: If $ I \subsetneqq J$ are ideals in $R$, then $ I^n \subsetneqq J^n$ for all $ n\geq 1$. We define the notion of a big ideal (Definition 1.2). It is noted that the property has close relationship with the notions of reduction of an ideal and Ratliff-Rush ideal [7]. Apart from other results, it is proved that a Noetherian domain satifies the property if and only if every ideal in $R$ is a Ratliff-Rush ideal. We also prove that ideals having no proper reduction are big ideals, and maximal ideals in regular rings ar…

约化数的界与滤链的Hilbert系数

Bounding reduction number and the Hilbert coefficients of filtration

本文研究了Cohen-Macaulay局部环上滤链的第三Hilbert系数的界，证明了在特定边界条件下Ratliff-Rush滤链的相伴分次环性质、约化数界及正则指数等结论。

二维理想幂的Hilbert-Kunz重数

Hilbert-Kunz multiplicity of powers of ideals in dimension two

本文研究二维局部环中理想幂的Hilbert-Kunz重数，解答了Smirnov的问题，并利用Ratliff-Rush版本给出判定准则。

On reduction numbers and Castelnuovo-Mumford regularity of blowup rings and modules

We prove new results on the connections between reduction numbers and the Castelnuovo-Mumford regularity of blowup algebras and blowup modules, the key basic tool being the operation of Ratliff-Rush closure. First, we answer in two particular cases a question of M. E. Rossi, D. T. Trung, and N. V. Trung about Rees algebras of ideals in two-dimensional Buchsbaum local rings, and we even ask whether one of such situations always holds. In another theorem we generalize a result of A. Mafi on ideals in two-dimensional Cohen-Macaulay local rings, by extending it to arbitrary dimension (and allowing…

On Coefficient ideals

Let $(A,\mathfrak{m})$ be a Cohen-Macaulay local ring of dimension $d \geq 2$ with infinite residue field and let $I$ be an $\mathfrak{m}$-primary ideal. For $0 \leq i \leq d$ let $I_i$ be the $i^{th}$-coefficient ideal of $I$. Also let $\widetilde{I} = I_d$ denote the Ratliff-Rush closure of $A$. Let $G = G_I(A)$ be the associated graded ring of $I$. We show that if $\dim H^j_{G_+}(G)^\vee \leq j -1$ for $1 \leq j \leq i \leq d-1$ then $(I^n)_{d-i} = \widetilde{I^n}$ for all $n \geq 1$. In particular if $G$ is generalized Cohen-Macaulay then $(I^n)_1 = \widetilde{I^n}$ for all $n \geq 1$. As …

Dao关于 fullness 渐近行为的问题

Dao's question on the asymptotic behaviour of fullness

本文针对Dao提出的局部环中理想fullness性质渐近行为控制问题，利用约化数、Ratliff-Rush闭包和Rees代数正则性等工具，建立了相关不变量的上界及部分精确公式。

Über die von einem Ideal $I \subset R$ erzeugten $R$-Moduln

Let $(R, \mathfrak m)$ be a commutative noetherian local ring. We investigate under which conditions an $R$-module $M$ is generated by an ideal $I$, i.e. there exists an epimorphism $I^{(Λ)} \twoheadrightarrow M$. If $M$ is uniserial, i.e. $\mathcal{L}(M)$ is totally ordered and finite, this is equivalent to $\mathfrak{m}^{n-1} \cdot I \not\subset \operatorname{Ann}_R(M) \cdot I$ ($\operatorname{length}(M) = n \geq 1$). If $M$ is cyclic and $I = \mathfrak{m}$, this is equivalent to: Either it is $M \cong R/\mathfrak{p}$ ($R/\mathfrak{p}$ a discrete valuation ring) or $M \cong C/\operatorname{S…

Vanishing of Tors of absolute integral closures in equicharacteristic zero

We show that a ring $R$ is regular if $Tor_{i}^{R}(R^{+},k) = 0$ for some $i\geq 1$ assuming further that $R$ is a $\mathbb{N}$-graded ring of dimension $2$ finitely generated over an equi-characteristic zero field $k$. This answers a question of Bhatt, Iyengar, and Ma. We use almost mathematics over $R^{+}$ to deduce properties of the noetherian ring $R$ and rational surface singularities. Moreover we show that $R^{+}$ in equi-characteristic zero is $m$-adically ideal(wise) separated, a condition which appears in the proof of local criterion for flatness. In dimension $2$ it is Ohm-Rush and i…