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在他关于交换诺特局部环 $R$上模的syzygy模的Bass级数的工作中,Lescot引入了一个数值不变量,记为 $\sigma(R)$,并询问对于任何 $R$是否它是有限的。 他证明了当 $R$是Gorenstein或Golod时,这是成立的。 在本工作中,许多新的环类 $R$被确定,对于这些环, $\sigma(R)$是有限的。 新的洞察是$\sigma(R)$与从模的通常上同调到其稳定上同调的自然映射有关,这允许使用乘法结构来研究$\sigma(R)$的有限性问题。
In his work on the Bass series of syzygy modules of modules over a commutative noetherian local ring $R$, Lescot introduces a numerical invariant, denoted $\sigma(R)$, and asks whether it is finite for any $R$. He proves that this is so when $R$ is Gorenstein or Golod. In the present work many new classes of rings $R$ for which $\sigma(R)$ is finite are identified. The new insight is that $\sigma(R)$ is related to the natural map from the usual cohomology of the module to its stable cohomology, which permits the use of multiplicative structures to study the question of finiteness of $\sigma(R)$.
We study the number $O_d$ of finite $O$-sequences of a given multiplicity $d$, with particular attention to the computation of $O_d$. We show that the sequence $(O_d)_d$ is sub-Fibonacci, and that if the sequence $(O_d / O_{d-1})_d$ converges, its limit is bounded above by the golden ratio. This analysis also produces an elementary method for computing $O_d$. 此外,我们通过利用S. Linusson在先前工作中引入的字典序段理想的分解,推导出$O_d$的一个迭代公式。
We study the number $O_d$ of finite $O$-sequences of a given multiplicity $d$, with particular attention to the computation of $O_d$. We show that the sequence $(O_d)_d$ is sub-Fibonacci, and that if the sequence $(O_d / O_{d-1})_d$ converges, its limit is bounded above by the golden ratio. This analysis also produces an elementary method for computing $O_d$. In addition, we derive an iterative formula for $O_d$ by exploiting a decomposition of lex-segment ideals introduced by S. Linusson in a previous work.
线性分解和更强的线性商性质是单项式理想的重要属性。 在本文中,我们根据单项式理想的lcm格完全表征了线性分解和线性商。 这些结果补充了根据相应Stanley-Reisner单纯复形的Alexander对偶来表征这两个性质的描述。 此外,我们讨论了边理想的情况下的应用。
Linear resolutions and the stronger notion of linear quotients are important properties of monomial ideals. In this paper, we fully characterize linear resolutions and linear quotients in terms of the lcm-lattice of monomial ideals. These results complement characterizations of these two properties in terms of the Alexander dual of the corresponding Stanley-Reisner simplicial complex. In addition, we discuss applications to the case of edge ideals.
设 $S=K[x_1,\ldots,x_n]$ 为在任意域 $K$ 上的 $n$ 个变量的多项式环。 给定一个有限生成的多分次模 $M$,其 斯坦利长度,记为 $\operatorname{slength}(M)$,是 $M$ 的斯坦利分解的最小长度。 设$I\subset S$是一个单项式理想,由$m$个单项式极小生成。 我们给出了$\operatorname{slength}(I)$的一个上界,以它的极小单项式生成元表示。 此外,如果我们知道$n=2$或者$m=2$,则给出了$\operatorname{slength}(I)$的精确公式。 此外,我们证明如果$I$有线性商,则$\operatorname{slength}(I)=m$,并且在某些特殊情况下逆命题成立。
Let $S=K[x_1,\ldots,x_n]$ be the ring of polynomials in $n$ variables over an arbitrary field $K$. Given a finitely generated multigraded module $M$, its Stanley length, denoted by $\operatorname{slength}(M)$, is the minimal length of a Stanley decomposition of $M$. Let $I\subset S$ be a monomial ideal, minimally generated by $m$ monomials. We give an upper bound for $\operatorname{slength}(I)$, in terms of its minimal monomial generators. Also, we give precise formulas for $\operatorname{slength}(I)$, if $n=2$ or $m=2$. Also, we show that if $I$ has linear quotients, then $\operatorname{slength}(I)=m$, and the converse holds in some special cases.