Carla Mascia, Giancarlo Rinaldo
We provide the regularity and the Cohen-Macaulay type of binomial edge ideals of Cohen-Macaulay cones, and we show the extremal Betti numbers of some classes of Cohen-Macaulay binomial edge ideals: Cohen-Macaulay bipartite and fan graphs. In addition, we compute the Hilbert-Poincaré series of the binomial edge ideals of some Cohen-Macaulay bipartite graphs.
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In this paper, we show that almost Cohen-Macaulay algebras are solid and in this respect, we seek for some special situation when (a) an almost Cohen-Macaulay algebra will be phantom extension and (b) when it maps into a balanced big Cohen-Macaulay module.
About the Cohen-Macaulay defect and almost Cohen-Macaulay rings
本文揭示了几乎Cohen-Macaulay环与Cohen-Macaulay亏格的联系，并引入一种Serre型条件，该条件与亏格的关系类似于$(S_n)$条件与Cohen-Macaulay模的关系。
On Sequentially Cohen-Macaulay Modules
本文给出了序列Cohen-Macaulay模的参数系刻画，推广了Cohen-Macaulay模和广义Cohen-Macaulay模的一些著名结果.研究了小嵌入维数的Stanley-Reisner环的序列Cohen-Macaulay性。
In this paper, we introduce and study the notion of linkage by perfect modules, which we call perfect linkage, for Cohen-Macaulay modules over Cohen--Macaulay local rings. We explore perfect linkage in connection with syzygies, maximal Cohen-Macaulay approximations and Yoshino-Isogawa linkage. We recover a theorem of Yoshino and Isogawa, and analyze the structure of double perfect linkage. Moreover, we establish a criterion for two Cohen-Macaulay modules of codimension one to be perfectly linked, and apply it to the classical linkage theory for ideals. We also construct various examples of lin…
Direct limits of Cohen-Macaulay rings
设$A$是Cohen-Macaulay环的直系的直极限.本文描述了$A$的Cohen-Macaulay性质。我们的结果表明，$A$不一定是Cohen-Macaulay。我们证明了$A$是Cohen-Macaulay在各种假设下。作为应用，我们研究了非仿射法线半群环的科恩-麦考莱性。
On sequentially Cohen-Macaulay modules and sequentially generalized Cohen-Macaulay modules
本文引入序列序列和序列f-序列，刻画了序列Cohen-Macaulay模与序列广义Cohen-Macaulay模，并给出了Cohen-Macaulay模的新刻画。
In \cite{AB}, the dagger closure is extended over finitely generated modules over Noetherian local domain $(R,\fm)$ and it is proved to be a Dietz closure. In this short note we show that it also satisfies the `Algebra axiom' of \cite{R.G} and this leads to the following result of this paper: For a complete Noetherian local domain, if it is contained in an almost Cohen-Macaulay domain, then there exists a balanced big Cohen-Macaulay algebra over it.
Dual Bass Numbers and Co-Cohen Macaulay Modules
本文利用模的对偶Bass数的消失性质给出了余-Cohen-Macaulay模的一个刻画。另外，我们证明了在一定条件下，余-Cohen Macaulay模的余局部化保持了余-Cohen Macaulay性。
Computing families of Cohen-Macaulay and Gorenstein rings
刻画了由某些类型的凸体半群得到的Cohen-Macaulay环和Gorenstein环.给出了判定多边形半群或圆半群是Cohen-Macaulay/Gorenstein半群的数学方法。我们也给出了Cohen-Macaulay环和Gorenstein环的一些族。
We introduce new homological dimensions, namely the Cohen-Macaulay projective, injective and flat dimensions for homologically bounded complexes. Among other things we show that (a) these invariants characterize the Cohen-Macaulay property for local rings, (b) Cohen-Macaulay flat dimension fits between the Gorenstein flat dimension and the large restricted flat dimension, and (c) Cohen-Macaulay injective dimension fits between the Gorenstein injective dimension and the Chouinard invariant.
The Cohen-Macaulay property of a graph arising from a poset has been studied by various authors. In this article, we study the Cohen-Macaulay property of a graph arising from a family of reflexive and antisymmetric relations on a set. We use this result to find classes of multipartite graphs which are Cohen-Macaulay.
On the discrete counterparts of Cohen-Macaulay algebras with straightening laws
研究了生成具有拉直律的Cohen-Macaulay代数（简称ASL）的偏序集的性质。证明了如果偏序集$P$生成Cohen-Macaulay ASL，则$P$是纯偏序集;如果$P$是Buchsbaum偏序集，则$P$是Cohen-Macaulay偏序集.还建立了关于由拉直闭理想定义的ASL的Rees代数的一些结果。证明了若$P$是具有唯一极小元的Cohen-Macaulay偏序集，且$Q$是$P$的偏序集理想，则$P\uplus Q$也是Cohen-Macaulay.
The third named author and Pérez proved that under certain conditions the test ideal of a module closure agrees with the trace ideal of the module closure. We use this fact to compute the test ideals of various rings with respect to the closures coming from their indecomposable maximal Cohen-Macaulay modules. We also give an easier way to compute the test ideal of a hypersurface ring in 3 variables coming from a module with a particular type of matrix factorization.
A finitely generated module $M$ over a commutative Noetherian ring $R$ is called an $I$-Cohen Macaulay module, if \[ \grade(I,M) + \dim(M/IM)= \dim(M), \] where $I$ is a proper ideal of $R$. The aim of this paper is to study the structure of this class of modules. It is discovered that $I$-Cohen Macaulay modules enjoy many interesting properties which are analogous to those of Cohen Macaulay modules. Also, various characterizations of $I$-Cohen Macaulay modules are presented here.
Non-Gorenstein isolated singularities of graded countable Cohen-Macaulay type
本文给出了C. Huneke和G. Leuschke（2003年）：设R是分次可数Cohen-Macaulay表示型的标准分次Cohen-Macaulay环，且R有一个孤立奇点.那么R必然是分次有限Cohen-Macaulay表示型吗？特别地，这个问题对于标准分次非Gorenstein环以及标准分次最小重数Gorenstein环都有肯定的答案。在此基础上，我们得到了分次可数Cohen-Macaulay型的分次Cohen-Macaulay环的一个部分分类。
Cohen-Macaulay injective, projective, and flat dimension
我们定义了三个新的同调维度-科恩-麦考利内射，投射，平坦的维度-居住在一个理论类似的经典内射，投射，平坦的维度。具有对偶模的Cohen-Macaulay环的新维数的等价性。
We investigate the presence of Cohen-Macaulay ideals in invariant rings and show that an ideal of an invariant ring corresponding to a modular representation of a $p$-group is not Cohen-Macaulay unless the invariant ring itself is. As an intermediate result, we obtain that non-Cohen-Macaulay factorial rings cannot contain Cohen-Macaulay ideals. For modular cyclic groups of prime order, we show that the quotient of the invariant ring modulo the transfer ideal is always Cohen-Macaulay, extending a result of Fleischmann.
On Frobenius Betti numbers of graded rings of finite Cohen-Macaulay type
针对环的Frobenius Betti数显式计算场景极少的问题，本文聚焦于有限Cohen-Macaulay型Cohen-Macaulay分次环，开展其Frobenius Betti数的显式计算研究，拓展该奇异性不变量的计算范围。
Let $(A,\mathfrak{m})$ be a Henselian Cohen-Macaulay local ring and let CM(A) be the category of maximal Cohen-Macaulay $A$-modules. We construct $T \colon CM(A)\times CM(A) \rightarrow mod(A)$, a subfunctor of $Ext^1_A(-, -)$ and use it to study properties of associated graded modules over $G(A) = \bigoplus_{n\geq 0} \mathfrak{m}^n/\mathfrak{m}^{n+1}$, the associated graded ring of $A$. As an application we give several examples of complete Cohen-Macaulay local rings $A$ with $G(A)$ Cohen-Macaulay and having distinct indecomposable maximal Cohen-Macaulay modules $M_n$ with $G(M_n)$ Cohen-Maca…
Let $R$ be a Cohen-Macaulay local ring, $I$ a strongly Cohen-Macaulay ideal of $R$. We show that $R/{\rm Ann}_R(I)$ is a maximal Cohen-Macaulay $R$-module by means of the delta-invariant. Also it is shown that there exists a Cohen-Macaulay ideal $J$ of $R$ such that the $δ_{R/J}$-invariant of all Koszul homologies of $R$ with respect $I$ is zero.
Super-stretched and graded countable Cohen-Macaulay type
定义了Cohen-Macaulay环的超拉伸性，证明了分次可数Cohen-Macaulay型的Cohen-Macaulay环是超拉伸的.我们利用这个结果证明了分次可数Cohen-Macaulay型正维数环有可能的h-向量（1），（1，n），或（1，n，1）。此外，一维标准分次Gorenstein环的分次可数型被证明是超曲面;这一结果是不知道在更高的维度。在非Gorenstein情形下，证明了维数大于2的分次可数Cohen-Macaulay型环具有极小重数.
Higher Cohen-Macaulay property of squarefree modules and simplicial posets
最近，G. Floystad研究了某些有限正则胞腔复形的“高阶Cohen-Macaulay性质”。本文将他的结果部分推广到无平方模、复曲面环和单纯偏序集。例如，我们证明了，如果一个单纯偏序集（的相应胞腔复形）是$l$ -Cohen-Macaulay，那么它的余维1骨架是$(l+1)$ -Cohen-Macaulay。
Cohen-Macaulay classes which are not conic
本文给出两个例子，证明了对于仿射半群环，Cohen-Macaulay类的集合可以大于锥类的集合。
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 coho…
In this note, we study the Cohen-Macaulayness of non-Noetherian rings. We show that Hochster's celebrated theorem that a finitely generated normal semigroup ring is Cohen-Macaulay does not extend to non-Noetherian rings. We also show that for any valuation domain $V$ of finite Krull dimension, $V[x]$ is Cohen-Macaulay in the sense of Hamilton-Marley.
Stanley--Reisner rings with large multiplicities are Cohen--Macaulay
利用Alexander对偶证明了一类具有足够大重数的Stanley-Reisner环是Cohen-Macaulay环.
Let $K$ be a field and $S=K[x_1,\ldots,x_m, y_1,\ldots,y_n]$ be the standard bigraded polynomial ring over $K$. In this paper, we explicitly describe the structure of finitely generated bigraded "sequentially Cohen--Macaulay" $S$-modules with respect to $Q=(y_1,\ldots,y_n)$. Next, we give a characterization of sequentially Cohen--Macaulay modules with respect to $Q$ in terms of local cohomology modules. Cohen--Macaulay modules that are sequentially Cohen--Macaulay with respect to $Q$ are considered.
We prove that sequentially Cohen-Macaulay rings in positive characteristic, as well as sequentially Cohen-Macaulay Stanley-Reisner rings in any characteristic, have trivial Lyubeznik table. Some other configurations of Lyubeznik tables are also provided depending on the deficiency modules of the ring.
Arithmetical rank of Cohen-Macaulay squarefree monomial ideals of height two
本文证明了一个高为2的无平方根单项式理想，其商环为Cohen-Macaulay，是集论完全交.
Local rings of countable Cohen--Macaulay type
本文证明了Schreyer猜想的一个极好的情形：具有可数Cohen-Macaulay型的局部环至多有一个一维奇异轨迹.进一步证明了可数CM型Cohen-Macaulay局部环的局部化也是可数CM型的。
More properties of almost Cohen-Macaulay rings
研究了几乎Cohen-Macaulay环的一些有趣的性质，并研究了与这类环有关的一个Serre型性质.
Cohen-Macaulayness of large powers of Stanley-Reisner ideals
证明了当m > 2时，Stanley-Reisner理想的m次符号幂是Cohen-Macaulay当且仅当单纯复形是拟阵.类似地，m次普通幂是Cohen-Macaulay，其中m > 2当且仅当复形是完全交。这些结果解决了Stanley-Reisner理想的普通幂和符号幂的Cohen-Macaulay性的几个公开问题。此外，它们对刻面理想和覆盖理想的象征力量的Cohen-Macaulayness有有趣的影响。
On two dimensional mixed characteristic rings of finite Cohen Macaulay type
本文给出了二维有限Cohen-Macaulay型混合特征环的大量例子。对于这些例子的一个大子类，我们给出了它的不可分解极大Cohen-Macaulay模的完整描述，并计算了它的AR-模。
In this paper, we study the two different topics related to sequentially Cohen-Macaulay modules. The questions are when the sequentially Cohen-Macaulay property preserve the localization and the module-finite extension of rings.
The Cohen-Macaulay type of idealizations of maximal Cohen-Macaulay modules over Cohen-Macaulay local rings is explored. There are two extremal cases, one of which is closely related to the theory of Ulrich modules \cite{BHU, GOTWY1, GOTWY2, GTT2}, and the other one is closely related to the theory of residually faithful modules and the theory of closed ideals \cite{BV}.
Classes of sequentially Cohen-Macaulay squarefree monomial ideals
我们计算了完全无平方lexsegment理想的最小准素分解。我们证明了临界无平方根单项理想是序列Cohen-Macaulay理想。作为应用，我们给出了序列Cohen-Macaulay的完全无平方lexsegment理想的一个完整刻画，并导出了这类理想的一些同调不变量的计算公式.
On approximately Cohen-Macaulay binomial edge ideal
文[4]引入了图G的二项边理想IG。他们发现了一些类的图G的性质，即IG是一个科恩-麦考利理想。这可能只发生在少数几类图上。科恩-麦考利的一种推广，称为近似科恩-麦考利，是由S。Goto在[3]中。研究了一类二项式边理想近似Cohen-Macaulay的图。此外，我们使用一些同调的方法来计算它们的希尔伯特级数。
Sequentially Cohen-Macaulay monomial ideals of embedding dimension four
设$I$是域$K$上多项式环$S=K[x_1,...,x_4]$的单项理想.然后$S/I$是顺序的Cohen-Macaulay当且仅当$S/I$是非常干净的。特别地，如果$S/I$是顺序Cohen-Macaulay，则$I$是Stanley理想。
We investigate the behavior of Cohen-Macaulay defect undertaking tensor product with a perfect module. Consequently, we study the perfect defect of a module. As an application, we connect to associated prime ideals of tensor products.
This paper shows that Cohen-Macaulay algebras can be algebraically approximated in such a way that their Cohen-Macaulayness and minimal Betti numbers are preserved. This is achieved by showing that finitely generated modules over power series rings can be algebraically approximated in a manner that preserves their diagrams of initial exponents and their minimal Betti numbers. These results are also applied to obtain an approximation result for flat homomorphisms from rings of power series to Cohen-Macaulay algebras.
Let $M$ be an $R$-module over a Noetherian ring $R$ and $\mathfrak{a}$ be an ideal of $R$ with $c={\rm cd}(\mathfrak{a},M)$. First, we prove that $M$ is finite $\mathfrak{a}$-relative Cohen-Macaulay if and only if ${\rm H}_i(Λ_{\mathfrak{a}}({\rm H}_{\mathfrak{a}}^c(M)))=0$ for all $i\neq c$ and ${\rm H}_c(Λ_{\mathfrak{a}}({\rm H}_{\mathfrak{a}}^c(M))) \cong \widehat{M}^{\mathfrak{a}}$. Next, over an $\mathfrak{a}$-relative Cohen-Macaulay local ring $(R,\mathfrak{m})$, we provide a characterization of $\mathfrak{a}$-relative sequentially Cohen-Macaulay modules $M$ in terms of $\mathfrak{a}$-re…
In this paper we determine the possible Hilbert functions of a Cohen-Macaulay local ring of dimension $d$, multiplicity $e$ and first Hilbert coefficient $e_1$ in the case $e_1 = e + 2$.
This paper shows that if $R$ is a homomorphic image of a Cohen-Macaulay local ring, then $R$-module $M$ is sequentially generalized Cohen-Macaulay if and only if the difference between Hilbert coefficients and arithmetic degrees for all distinguished parameter ideals of $M$ are bounded.
It is shown that a module is sequentially Cohen-Macaulay if and only if the index of reducibility for distinguished parameter ideals are eventually constant with special value. As corollaries to the main theorem we given to characterize the Gorensteinness, Cohen-Macaulayness of local rings in term of eventually index of reducibility for distinguished parameter ideals.
Over a commutative local Cohen--Macaulay ring, we view and study the category of maximal Cohen--Macaulay modules as a ring with several objects. We compute the global dimension of this category and thereby extend a result of Leuschke to the case where the ring has arbitrary (as opposed to finite) CM-type.
Cohen-Macaulay Loci of modules
研究了Noether局部环$A$上任意有限模的Cohen-Macaulay轨迹，证明了在某些情形下它是$\Spec A$的Zerkiki-开子集.在这方面，环的形式纤维在某些素理想是Cohen-Macaulay的研究。
Cohen-Macaulayness of bipartite graphs, revisited
二部图的Cohen-Macaulay性是由几个数学家研究的，并已得到了组合刻画。本文给出了二部图的Cohen-Macaulay性的几个不同的组合条件。在以前的作品中的条件是依赖于一个适当的排序图的顶点。本文中提出的条件不依赖于任何排序。最后，我们给出了一个判定给定二部图的Cohen-Macaulay性的快速算法。
Unmixed and sequentially Cohen-Macaulay skew tableau ideals
本文研究由正整数填充斜 Ferrers 图所定义的斜表理想，完成了对无混与序列 Cohen–Macaulay 情形的分类，并据此得到 Cohen–Macaulay、Buchsbaum 和广义 Cohen–Macaulay 情形的完整分类。
Uniform bounds in generalized Cohen-Macaulay rings
建立了广义Cohen-Macaulay环中参数理想的相伴分次环的Castelnuovo-Mumford正则性的一致界.作为结果，我们得到了关系类型和假设数的统一界。此外，我们还证明了广义Cohen-Macaulay环可以用这种一致界的存在性来刻画。
We prove some results on the non-existence of rank one maximal Cohen-Macaulay modules over certain Segre product rings. As an application we show that over these Segre product rings there do not exist maximal Cohen-Macaulay modules with multiplicity less than or equal to the parameter degree of the ring, which disproves a conjecture of Schoutens.
Big Cohen-Macaulay Algebras and Seeds
我们深入研究代数所拥有的属性，我们称之为种子，映射到大科恩-麦考利代数。我们将证明在一个正特征的完备局部区域上，任意两个大Cohen-Macaulay代数映射到一个公共的大Cohen-Macaulay代数。我们也将加强Hochster和Huneke的“弱函子”存在性结果大Cohen-Macaulay代数的种子性质是稳定的基础下的变化之间的完整的局部区域的正特征。我们还证明了正特征局部环（R，m）上的每一个种子映射到一个大的Cohen-Macaulay R-代数，该代数是一个绝对整闭的m-根分离的拟局部整环.
Over a Cohen-Macaulay (CM) local ring, we characterize those modules that can be obtained as a direct limit of finitely generated maximal CM modules. We point out two consequences of this characterization: (1) Every balanced big CM module, in the sense of Hochster, can be written as a direct limit of small CM modules. In analogy with Govorov and Lazard's characterization of flat modules as direct limits of finitely generated free modules, one can view this as a "structure theorem" for balanced big CM modules. (2) Every finitely generated module has a preenvelope with respect to the class of fi…
In this paper, we investigate the maximal Cohen-Macaulay property of tensor products of modules, and then give criteria for projectivity of modules in terms of vanishing of Ext modules. One of the applications shows that the Auslander-Reiten conjecture holds for Cohen-Macaulay normal rings.
Using the theory of cohomology annihilators, we define a family of topologies on the set of isomorphism classes of maximal Cohen-Macaulay modules over a Gorenstein ring. We study compactness of these topologies.
Hypersurfaces of bounded Cohen--Macaulay type
令R = k[[x_0，.，x_d]]/（f），其中k是域，f是形式幂级数环k[[x_0，.，x_d]]。我们调查的问题，这种形式的环有界科恩-麦考利型，也就是说，有一个限制的重不可分解的极大科恩-麦考利模块。与有限Cohen-Macaulay型一样，如果特征不同于2，则问题简化为一维情况：环R具有有界Cohen-Macaulay型当且仅当R同构于k[[x_0，...，x_d]]/（g+x_2^2+.+ x_d^2），其中g是k[[x_0，x_1]]中的元素，且k[[x_0，x_1]]/（g）具有有界Cohen-Macaulay型.本文确定了形式为k[[x_0，x_1]]/（g）的环具有有界的Cohen-Macaulay型.
A natural extension of bipartite graphs are $d$-partite clutters, where $d \geq 2$ is an integer. For a poset $P$, Ene, Herzog and Mohammadi introduced the $d$-partite clutter $\mathcal{C}_{P,d}$ of multichains of length $d$ in $P$, showing that it is Cohen-Macaulay. We prove that the cover ideal of $\mathcal{C}_{P,d}$ admits an $x_i$-splitting, determining a recursive formula for its Betti numbers and generalizing a result of Francisco, Hà and Van Tuyl on the cover ideal of Cohen-Macaulay bipartite graphs. Moreover we prove a Betti splitting result for the Alexander dual of a Cohen-Macaulay s…
A new characterization of Cohen-Macaulay rings
本文的目的是给出Cohen-Macaulay局部环的一个新的刻划.作为结果，我们推出局部（Noether）环$R$是Gorenstein当且仅当$R$的每个参数理想都是不可约的.
The Cohen-Macaulay property of separating invariants of finite groups
在有限群的情况下，分离代数是分离轨道的不变量环的子代数。虽然分离代数往往表现得比环的不变量，我们表明，许多标准，这意味着环的不变量是非科恩-麦考利实际上意味着没有分次分离代数是科恩-麦考利。例如，我们表明，在一个领域的正特征p，给予足够多的副本的忠实模表示，没有分次分离代数是科恩-麦考利。进一步证明了对于p-群，Cohen-Macaulay分次分离代数的存在性意味着该群是由双反射生成的。进一步证明了对于$p$ -群，Cohen-Macaulay分次分离代数的存在性意味着该群是由双反射生成的.另外，我们给出了一个例子，证明了当不变量环不是Cohen-Macaulay时，Cohen-Macaulay分离代数也存在。
Lexsegment ideals are sequentially Cohen-Macaulay
确定了任意lexsegment理想$I\subset S=K[x_1,...,x_n]$的相关素数.作为应用，证明了$S/I$是一个相当干净的模，因此，$S/I$是顺序Cohen-Macaulay模，满足Stanley猜想.
Let $R = k[x_1,\ldots, x_n]$ be the polynomial ring in $n$ variables over a field $k$ and let $I$ be a monomial ideal of $R$. In this paper, we study almost Cohen-Macaulay simplicial complex. Moreover, we characterize the almost Cohen-Macaulay polymatroidal Veronese type and transversal polymatroidal ideals and furthermore we give some examples.
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