Masoud Tousi, Siamak Yassemi
In this paper we solve a problem, originally raised by Grothendieck, on the properties, i.e. Complete intersection, Gorenstein, Cohen--Macaulay, that are conserved under tensor product of algebras over a field $k$.
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Low-Rank Reduced Biquaternion Tensor Ring Decomposition and Tensor Completion
本文定义 RBTR 分解并给出 RBTR-SVD 算法，进一步结合 RBTR 秩与 TV 正则化提出 RBTR-TV 低秩张量补全方法，实验表明其在彩色图像和视频补全中具有优势。
AF-rings are algebras over a field k which satisfy the Altitude Formula over k. This paper surveys a few works in the literature on the Krull and valuative dimensions of tensor products of AF-rings. The first section extends Wadsworth's classical results on the Krull dimension of AF-domains to the larger class of AF-rings. It also provides formulas for computing the valuative dimension with effect on the transfer of the (locally) Jaffard property. The second section studies tensor products of AF-rings over a zero-dimensional ring. Most results on algebras over a field are extended to these gen…
This works concerns cohomological support varieties of modules over commutative local rings. The main result is that the support of a derived tensor product of a pair of differential graded modules over a Koszul complex is the join of the supports of the modules. This generalizes, and gives another proof of, a result of Dao and the third author dealing with Tor-independent modules over complete intersection rings. The result for Koszul complexes has a broader applicability, including to exterior algebras over local rings.
Let R be a commutative Noetherian domain, and let M and N be finitely generated R-modules. We give new criteria for determining when M tensor N has torsion. We also give constructive formulas for producing a module in the isomorphism class of the torsion submodule of M tensor N. In some cases we determine bounds on the length and minimal number of generators of this module. We focus on the case where R is a numerical semigroup ring with the goal of making progress on the Huneke-Wiegand Conjecture.
Our main goal in this paper is to set the general frame for studying the dimension theory of tensor products of algebras over an arbitrary ring $R$. Actually, we translate the theory initiated by A. Grothendieck and R. Sharp and subsequently developed by A. Wadsworth on Krull dimension of tensor products of algebras over a field $k$ into the general setting of algebras over an arbitrary ring $R$. For this sake, we introduce and study the notion of a fibred AF-ring over a ring $R$. This concept extends naturally the notion of AF-ring over a field introduced by A. Wadsworth in \cite{W} to algebr…
Let E and G be free modules of rank e and g, respectively, over a commutative noetherian ring R. The identity map on E^* tensor G induces the Koszul complex ... -> S_mE^* tensor S_nG tensor Wedge^p(E^* tensor G) -> S_{m+1}E^* tensor S_{n+1}G tensor Wedge^{p-1}(E^* tensor G) -> ... and its dual ... -> D_{m+1}E tensor D_{n+1}G^* tensor Wedge^{p-1}(E tensor G^*) -> D_mE tensor D_nG^* tensor Wedge^p(E tensor G^*)-> ... Let H_{m,n,p} be the homology of the top complex at S_m tensor S_n tensor Wedge^p and H^{m,n,p} the homology of the bottom complex at D_m tensor D_n tensor Wedge^p. It is known that…
On the depth and reflexivity of tensor products
本文研究交换Noether局部环上同调有限复形的张量积深度，给出超曲面环上有限生成模的非零张量积为自反模的新条件，并借助Asgharzadeh的结果在附录中探讨超曲面环上素理想张量积的自反性。
In this paper we prove that the Hermite ring conjecture holds for valuation rings $V$, and the special liner group $SL_n(V[x])$ coincides with the group generated by elementary matrices $E_n(V[x])$ for $n\geq3$. For any arithmetical ring $R$ and $n\geq3$, we show $SL_n(R[x]) = SL_n(R)\cdot E_n(R[x])$.
For a standard graded ring $R$ of dimension $\geq 2$ over a perfect field of characteristic $p>0$ and a homogeneous ideal $I$ of finite colength, the HK density function of $R$ with respect to $I$ is a compactly supported continuous function $f_{R, I}:[0, \infty)\longto [0, \infty)$, whose integration yields the \mbox{HK} multiplicity $e_{HK}(R, I)$. Here we answer a question of V. Trivedi about the Hilbert-Kunz density function of the tensor product of standard graded rings and show that it is the convolution of the Hilbert-Kunz density function of the factor rings. Using Fourier transform, a…
A special subring of the Nagata ring and the Serre's conjecture ring
本文研究了Nagata环和Serre猜想环的一个特殊子环Anderson环的性质，并将其与原环进行比较。
In this paper, as an analogue of the spectrum of a tensor triangulated category introduced by Balmer, we define a spectrum of a triangulated category which does not necessarily admit a tensor structure. We apply it for some triangulated categories associated to a commutative noetherian ring.
Some descriptions of linked ideals in a commutative Notherian ring $R$ are provided in terms of the Associated prime ideals of $R$. Then, among other things, we make some characterization of Cohen-Macaulay, Gorenstein and regular local rings in terms of their linked ideals.
Construction of Gorenstein projective modules over tensor rings
本文给出张量环上完全投射分解和Gorenstein投射模的充要条件，并由此提供从基环构造张量环上Gorenstein投射模的方法，应用于平凡环扩张、Morita上下文环和三角矩阵环。
This paper is devoted to present some characterizations for a local ring to be generically Gorenstein and Gorenstein by means of $δ$-invariant and linkage theory.
Tensor products usually have nonzero torsion. This is a central theme of Auslander's paper "Modules over unramified regular local rings"; the theme continues in the work of Huneke and Wiegand. The main focus in this note is on tensor powers of a finitely generated module over a local ring. Also, we study torsion-free modules N with the property that its tensor product with any module M has torsion, unless M is very special. Important examples of such modules N are the Frobenius power of a ring, viewed as a module over itself, that is a complete intersection domain of positive characteristic.
In this article, we compute the regularity of Rees algebra of binomial edge ideals of closed graphs. We obtain a lower bound for the regularity of Rees algebra of binomial edge ideals. We also study some algebraic properties of the Rees algebra and special fiber ring of binomial edge ideals of closed graphs via algebraic properties of their initial algebra and Sagbi basis theory. We obtain an upper bound for the regularity of the special fiber ring of binomial edge ideals of closed graphs.
The depth of tensor product of modules over a Gorenstein local ring is studied. For finitely generated modules M and N over a Gorenstein local ring R, under some assumptions on the vanishing of finite number of Tate and relative homology modules, the depth($M\otimes N$) is determined in terms of the depth(M) and depth(N).
Gorenstein Special Fiber Rings of Ladder Determinantal Modules
本文研究了阶梯行列式模的特纤维环为Gorenstein的条件，通过分析底层矩阵的数据来确定其性质。
In this paper we solve a problem, originally raised by Grothendieck, on the transfer of Cohen-Macaulayness to tensor products of algebras over a field. As a prelude to this, we investigate the grade for some specific types of ideals that play a primordial role within the ideal structure of such constructions.
Endomorphism algebras over commutative rings and torsion in self tensor products
本文研究交换 Noetherian 局部环上有限生成模的自同态环作用下的张量积，证明在温和条件下不可分解模的自张量积必有挠元。
Quasilifting of hulls and depth of tensor product of modules
本文研究局部环上有限生成模的张量积深度，利用Huneke等人的提升构造，恢复相关结果、否定特定问题并建立下界，推导局部完全$\mathcal{TE}$环上的张量积深度结果，还研究了包络和逼近存在的一般条件。
We initiate the theory of graded commutative 2-rings, a categorification of graded commutative rings. The goal is to provide a systematic generalization of Paul Balmer's comparison maps between the spectrum of tensor-triangulated categories and the Zariski spectra of their central rings. By applying our constructions, we compute the spectrum of the derived category of perfect complexes over any graded commutative ring, and we associate to every scheme with an ample family of line bundles an embedding into the spectrum of an associated graded commutative 2-ring.
(projectively coresolved) Gorenstein flat modules over tensor rings
本文针对张量环结构，刻画了其上的投射余分解Gorenstein平坦模的等价判定条件，明确描述了一类相关平坦模，并给出了其在两类环结构上的应用。
We know that for a finite field $F$, every function on $F$ can be given by a polynomial with coefficients in $F$. What about the converse? i.e. if $R$ is a ring (not necessarily commutative or with unity) such that every function on $R$ can be given by a polynomial with coefficients in $R$, can we say $R$ is a finite field ? We show that the answer is yes, and that in fact it is enough to only require that all bijections be given by polynomials. If we allow our rings to have unity, we show that the property that all characteristic functions can be given by polynomials actually characterizes fi…
This paper establishes an analogue of the special chain theorem for the embedding dimension of polynomial rings, with direct application on the (embedding) codimension. In particular, we recover a classic result on the transfer of regularity to polynomial rings (initially proved via a combination of Serre's result on finite global dimension and Hilbert theorem on syzygies). A second application characterizes regularity in general settings of localizations of polynomial rings, including Nagata rings and Serre's conjecture rings.
In this article we consider the exterior power and the symmetric tensors of the polynomial ring in one variable. The structure of an associative semigraded algebra of this polynomial ring induces on the symmetric tensors the structure of an associative semigraded algebra, and on the exterior power induces structure of a semigraded module over semigraded algebra of symmetric tensors. The algebra of symmetric polynomials is isomorphic to the algebra of the symmetric tensors of polynomial ring in one variables. We obtained the explicit expression for symmetric polynomials via elementary symmetric…
In this paper, we study Serre's condition $(S_n)$ for tensor products of modules over a commutative noetherian local ring. The paper aims to show the following. Let $M$ and $N$ be finitely generated module over a commutative noetherian local ring $R$, either of which is $(n+1)$-Tor-rigid. If the tensor product $M \otimes_R N$ satisfies $(S_{n+1})$, then under some assumptions $\mathrm{Tor}_{i}^R(M, N) = 0$ for all $i \ge 1$. The key role is played by $(n+1)$-Tor-rigidity of modules. As applications, we will show that the result recovers several known results.
In this paper, we study the ring of invariants under the action of SL(m,K)\times SL(n,K) and SL(m,K)\times SL(n,K)\times SL(2,K) on the 3-dimensional array of indeterminates of form m\times n\times 2, where K is an infinite field. And we show that if m=n\geq 2, then the ring of SL(n,K)\times SL(n,K)-invariants is generated by n+1 algebraically independent elements over K and the action of SL(2,K) on that ring is identical with the one defined in the classical invariant theory of binary forms. We also reveal the ring of SL(m,K)\times SL(n,K)-invariants and SL(m,K)\times SL(n,K)\times SL(2,K)-in…
Invariant rings of the special orthogonal group have nonunimodal $h$-vectors
本文通过将特殊正交群不变环视为正交群不变环的循环覆盖，给出其 $F$-正则性的新证明，并据此证明其 $h$-向量不必单峰。
Let $(R, {\mathfrak m})$ be a Noetherian local ring and let $I$ be an $R$-ideal. Inspired by the work of Hübl and Huneke, we look for conditions that guarantee the Cohen-Macaulayness of the special fiber ring ${\mathcal F}={\mathcal R}/{\mathfrak m}{\mathcal R}$ of $I$, where ${\mathcal R}$ denotes the Rees algebra of $I$. Our key idea is to require `good' intersection properties as well as `few' homogeneous generating relations in low degrees. In particular, if $I$ is a strongly Cohen-Macaulay $R$-ideal with $G_{\ell}$ and the expected reduction number, we conclude that ${\mathcal F}$ is alwa…
On the $S$-version of some special elements in commutative rings
本文研究了交换环中若干基本元素的S版本，定义并探讨了S可逆、S幂等、S von Neumann 正则及S-π正则元素的性质，用于刻画环类，并关注布尔环和π-正则环的统一S版本，提供区分其经典类比的例子。
We define and characterise small support for complexes over non-Noetherian rings and in this context prove a vanishing theorem for modules. Our definition of support makes sense for any rigidly compactly generated tensor triangulated category. Working in this generality, we establish basic properties of support and investigate when it detects vanishing. We use pointless topology to relate support, the topology of the Balmer spectrum, and the structure of the idempotent Bousfield lattice.
The $h$-vectors of homogeneous rings are one of the most important invariants that often reflect ring-theoretic properties. On the other hand, there are few examples of edge rings of graphs whose $h$-vectors are explicitly computed. In this paper, we compute the $h$-vector of a special family of graphs, by using the technique of initial ideals and the associated simplicial complex.
This paper is concerned with the prime spectrum of a tensor product of algebras over a field. It seeks necessary and sufficient conditions for such a tensor product to have the S-property, strong S-property, and catenarity. Its main results lead to new examples of stably strong S-rings and universally catenarian rings. The work begins by investigating the minimal prime ideal structure. Throughout, several results on polynomial rings are recovered, and numerous examples are provided to illustrate the scope and sharpness of the results.
Torsion and complete dualizable objects in tensor-triangulated categories over a Noetherian ring
本文研究了在Noetherian环作用下张量三角范畴中的扭和完全可对偶对象，证明了其可被抽象重构，并探讨了强生成元与可代表性定理的关系。
In this paper firstly, we generalize the concept of codismantlable graphs to hypergraphs and show that some special vertex decomposable hypergraphs are codismantlable. Then we generalize the concept of bouquet in graphs to hypergraphs to extend some combinatorial invariants of graphs about disjointness of a set of bouquets. We use these invariants to characterize the projective dimension of Stanley-Reisner ring of special hypergraphs in some sense.
Christos Athanasiadis studies an effective technique to show that Gorenstein sequences coming from compressed polytopes are unimodal. In the present paper we will use such the technique to find a rich class of Gorenstein toric rings with unimodal $h$-vectors arising from finite graphs.
We consider the tensor product of modules over the polynomial algebra corresponding to the usual tensor product of linear operators. We present a general description of the representation ring in case the ground field k is perfect. It is made explicit in the special cases when k is real closed respectively algebraically closed. Furthermore, we discuss the generalisation of this problem to representations of quivers. In particular the representation ring of quivers of extended Dynkin type A is provided.
We give necessary and sufficient conditions for stratification and costratification to descend along a coproduct preserving, tensor-exact $R$-linear functor between $R$-linear tensor-triangulated categories which are rigidly-compactly generated by their tensor units. We then apply these results to non-positive commutative DG-rings and connective ring spectra. In particular, this gives a support-theoretic classification of (co)localizing subcategories, and thick subcategories of compact objects of the derived category of a non-positive commutative DG-ring with finite amplitude, and provides a f…
Let $R$ be a polynomial ring and $I \subset R$ be a perfect ideal of height two minimally generated by forms of the same degree. We provide a formula for the multiplicity of the saturated special fiber ring of $I$. Interestingly, this formula is equal to an elementary symmetric polynomial in terms of the degrees of the syzygies of $I$. Applying ideas introduced in arXiv:1805.05180, we obtain the value of the j-multiplicity of $I$ and an effective method for determining the degree and birationality of rational maps defined by homogeneous generators of $I$.
Let $R$ be a polynomial ring over a field and $I \subset R$ be a Gorenstein ideal of height three that is minimally generated by homogeneous polynomials of the same degree. We compute the multiplicity of the saturated special fiber ring of $I$. The obtained formula depends only on the number of variables of $R$, the minimal number of generators of $I$, and the degree of the syzygies of $I$. Applying results from arXiv:1805.05180, we get a formula for the $j$-multiplicity of $I$ and an effective method to study a rational map determined by a minimal set of generators of $I$.
Macaulay Posets and Rings
本文建立环与其单项式偏序集之间的麦考利对应定理，利用张量积与笛卡尔积的对应关系在环论与偏序集理论间传递结果，解决多个公开问题，并对树环张量积的麦考利环进行分类。
Improved Kunneth Tricks
本文提出了 Kunneth 技巧公式的两项改进，分别用于计算非正 DG 环上两个 DG 模的普通张量积与导出张量积的最高上同调，并给出了初等证明。
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