Updating Singular Value Decomposition for Rank One Matrix Perturbation

An efficient Singular Value Decomposition (SVD) algorithm is an important tool for distributed and streaming computation in big data problems. It is observed that update of singular vectors of a rank-1 perturbed matrix is similar to a Cauchy matrix-vector product. With this observation, in this paper, we present an efficient method for updating Singular Value Decomposition of rank-1 perturbed matrix in $O(n^2 \ \text{log}(\frac{1}{\epsilon}))$ time. The method uses Fast Multipole Method (FMM) for updating singular vectors in $O(n \ \text{log} (\frac{1}{\epsilon}))$ time, where $\epsilon$ is the precision of computation

On the local cohomology modules deffined by a pair of ideals and serre subcategories

This paper is concerned about the relation between local cohomology modules defined by a pair of ideals and Serre classes of R-modules, as a generalization of results of J. Azami, R. Naghipour and B. Vakili (2009) and M. Asgharzadeh and M.Tousi (2010). Let R be a commutative Noetherian ring, I, J be two ideals of R and M be an R-module. Let a\in \~{W}(I; J) and t \in N_0 be such that Ext^t_R(R/a,M)\in S and Ext^j_R(R/a,H^i_I;J(M))\inS for all i =0. Then for any submodule N of H^t_I;J(M) such that Ext^1_R(R/a;N)\in,we obtain HomR(R=a;H^t_I;J(M)/N)\inS.Comment: 12 page

Faltings' local-global principle for the in dimension <n\bf< n of local cohomology modules

The concept of Faltings' local-global principle for the in dimension $< n$ of local cohomology modules over a Noetherian ring $R$ is introduced, and it is shown that this principle holds at levels 1, 2. We also establish the same principle at all levels over an arbitrary Noetherian ring of dimension not exceeding 3. These generalize the main results of Brodmann et al. in \cite{BRS}. Moreover, as a generalization of Raghavan's result, we show that the Faltings' local-global principle for the in dimension $<n$ of local cohomology modules holds at all levels $r\in \mathbb{N}$ whenever the ring $R$ is a homomorphic image of a Noetherian Gorenstein ring. Finally, it is shown that if $M$ is a finitely generated $R$-module, $\frak a$ an ideal of $R$ and $r$ a non-negative integer such that $\frak a^tH^i_{\frak a}(M)$ is in dimension $< 2$ for all $i<r$ and for some positive integer $t$, then for any minimax submodule $N$ of $H^r_{\frak a}(M)$, the $R$-module \Hom_R(R/\frak a, H^r_{\frak a}(M)/N) is finitely generated. As a consequence, it follows that the associated primes of $H^r_{\frak a}(M)/N$ are finite. This generalizes the main results of Brodmann-Lashgari \cite{BL} and Quy \cite{Qu}.Comment: To appear in Communications in Algebra. arXiv admin note: substantial text overlap with arXiv:1308.554

On the Attached prime ideals of local cohomology modules defined by a pair of ideals

Let $I$ and $J$ be two ideals of a commutative Noetherian ring $R$ and $M$ be an $R$-module of dimension $d$. If $R$ is a complete local ring and $M$ is finite, then attached prime ideals of $H^{d-1}_{I,J}(M)$ are computed by means of the concept of co-localization. Also, we illustrate the attached prime ideals of $H^{t}_{I,J}(M)$ on a non-local ring $R$, for $t= \dim M$ and $t= cd(I,J,M)$.Comment: are welcome

On graded local cohomology modules defined by a pair of ideals

Let $R = \bigoplus_{n \in \mathbb{N}_{0}} R_{n}$ be a standard graded ring, $M$ be a finite graded $R$-module and $J$ be a homogenous ideal of $R$. In this paper we study the graded structure of the $i$-th local cohomology module of $M$ defined by a pair of ideals $(R_{+},J)$, i.e. $H^{i}_{R_{+},J}(M)$. More precisely, we discuss finiteness property and vanishing of the graded components $H^{i}_{R_{+},J}(M)_{n}$. Also, we study the Artinian property and tameness of certain submodules and quotient modules of $H^{i}_{R_{+},J}(M)$.Comment: are welcome

On top local cohomology modules, Matlis duality and tensor products

Let $\mathfrak{a}$ be an ideal of a local ring $(R, \mathfrak{m})$ with $c = \mathrm{cd}(\mathfrak{a},R)$ the cohomological dimension of $\mathfrak{a}$ in $R$. In the case that $c=\dim R$, we first give a bound for depth~$D(H^c_\mathfrak{a}(R))$, where $c>2$ and $(R,\mathfrak{m})$ is complete. Later, $H^c_\mathfrak{a}(R) \otimes_R H^c_\mathfrak{a}(R)$, $D(H^c_\mathfrak{a}(R)) \otimes_R D(H^c_\mathfrak{a}(R))$ and $H^c_\mathfrak{a}(R) \otimes_R D(H^c_\mathfrak{a}(R))$ are examined. In the case $c=\dim R-1$, the set Att$_R H^c_\mathfrak{a}(R)$ is considered.Comment: 12 pages, This is the extended version of arXiv:1302.1274v1 and arXiv:1212.0245. accepted to appear in Journal of Algebra and Its Application

On the associated prime ideals of local cohomology modules defined by a pair of ideals

Let $I$ and $J$ be two ideals of a commutative Noetherian ring $R$ and $M$ be an $R$-module. For a non-negative integer $n$ it is shown that, if the sets \Ass_R(\Ext^{n} _{R}(R/I,M)) and \Supp_R(\Ext^{i}_{R}(R/I,H^{j}_{I,J} (M))) are finite for all $i \leq n+1$ and all $j< n$, then so is \linebreak\Ass_R(\Hom_{R}(R/I,H^{n}_{I,J}(M))). We also study the finiteness of \Ass_R(\Ext^{i}_{R}(R/I,H^{n}_{I,J} (M))) for $i=1,2$.Comment: are welcome

Some homological properties of ideals with cohomological dimension one

Let R denote a commutative Noetherian ring and let I be an ideal of R such that H_i^I(R) = 0, for all integers i greater than or equal to 2. In this paper we shall prove some results concerning the homological properties of I

Upper bounds, cofiniteness, and artinianness of local cohomology modules defined by a pair of ideals

Let $R$ be a commutative noetherian ring, $I,J$ be two ideals of $R$, $M$ be an $R$-module, and $\mathcal{S}$ be a Serre class of $R$-modules. A positive answer to the Huneke$^,$s conjecture is given for a noetherian ring $R$ and minimax $R$-module $M$ of krull dimension less than 3, with respect to $\mathcal{S}$. There are some results on cofiniteness and artinianness of local cohomology modules with respect to a pair of ideals. For a ZD-module $M$ of finite krull dimension and an integer $n\in\mathbb{N}$, if \lc^{i}_{I,J}(M)\in\mathcal{S} for all $i>n$, then \lc^{i}_{I,J}(M)/\fa^{j}\lc^{i}_{I,J}(M)\in\mathcal{S} for any \fa\in\tilde{W}(I,J), all $i\geq n$, and all $j\geq0$. By introducing the concept of Seree cohomological dimension of $M$ with respect to $(I,J)$, for an integer $r\in\mathbb{N}_0$, \lc^{j}_{I,J}(R)\in\mathcal{S} for all $j>r$ iff \lc^{j}_{I,J}(M)\in\mathcal{S} for all $j>r$ and any finite $R$-module $M$.Comment: 13 page

Relative Cohen-Macaulay filtered modules with a view toward relative Cohen-Macaulay modules

Let R be a commutative Noetherian ring, a a proper ideal of R and M a finite R-module. It is shown that, if (R;m) is a complete local ring, then under certain conditions a contains a regular element on DR(Hc a(M)), where c = cd(a;M). A non-zerodivisor characterization of relative Cohen-Macaulay modules w.r.t a is given. We introduce the concept of relative Cohen-Macaulay filtered modules w.r.t a and study some basic properties of such modules. In paticular, we provide a non-zerodivisor characterization of relative Cohen-Macaulay filtered modules w.r.t a. Furthermore, a characterization of cohomological dimension filtration of M by the associated prime ideals of its factors is established. As a consequence, we present a cohomological dimension filtration for those modules whose zero submodule has a primary decomposition. Finally, we bring some new results about relative Cohen- Macaulay modules w.r.t a.Comment: 15 page