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arXiv 2204.03136math.ACmath.CO
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无平方单项式理想幂的单纯分解

Simplicial Resolutions of Powers of Square-free Monomial Ideals

Susan M. Cooper, Sabine El Khoury, Sara Faridi, Sarah Mayes-Tang, Susan Morey, Liana M. Sega, Sandra Spiroff

AI总结:

本文构造支撑任意无平方单项式理想幂自由分解的单纯复形,显著缩小 Taylor 分解,并通过极值理想给出更优 Betti 数上界。

摘要:

对于单项式理想的幂,Taylor分解几乎从来不是极小的,即使在无平方情形下也是如此。本文中,我们为任意无平方单项式理想的每个幂引入了一种更小的分解,该分解仅依赖于理想生成元的数量。更准确地说,对于每一对固定整数 $r$ 和 $q$,我们构造了一个单纯复形,它支撑具有 $q$ 个生成元的任意无平方单项式理想的 $r$ 次幂的自由分解。所得分解明显小于 Taylor 分解,并且在特殊情形下是极小的。考虑固定理想的生成元之间的关系使我们能够进一步缩小这些分解。我们还引入了一类称为“极值理想”的理想,并证明所有无平方单项式理想的幂的 Betti 数都以极值理想的幂的 Betti 数为界。我们的结果给出了任意无平方单项式理想的幂的 Betti 数的上界,这些上界极大地改进了 Taylor 分解所提供的二项式界。

英文摘要:

The Taylor resolution is almost never minimal for powers of monomial ideals, even in the square-free case. In this paper we introduce a smaller resolution for each power of any square-free monomial ideal, which depends only on the number of generators of the ideal. More precisely, for every pair of fixed integers $r$ and $q$, we construct a simplicial complex that supports a free resolution of the $r$-th power of any square-free monomial ideal with $q$ generators. The resulting resolution is significantly smaller than the Taylor resolution, and is minimal for special cases. Considering the relations on the generators of a fixed ideal allows us to further shrink these resolutions. We also introduce a class of ideals called "extremal ideals", and show that the Betti numbers of powers of all square-free monomial ideals are bounded by Betti numbers of powers of extremal ideals. Our results lead to upper bounds on Betti numbers of powers of any square-free monomial ideal that greatly improve the binomial bounds offered by the Taylor resolution.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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