arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2005.09991math.AC
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幂的生成元个数下降的某些单项理想

Certain monomial ideals whose numbers of generators of powers descend

Reza Abdolmaleki, Shinya Kumashiro

摘要:

本文研究了多项式环中单项理想的幂的极小生成元的个数。对于二元单式理想$I$,Eliahou,Herzog和Saem给出了一个关于$I^2$与$μ(I)\geq 6$的极小生成元个数的急剧下界$μ(I^2)\ge 9$.最近,Gasanova构造了单项式理想,使得对任意正整数$n$都有$μ(I)>μ(I^n)$.在此基础上,我们构造了一类单项式理想,使得对任意正整数$n$,$μ(I)>μ(I^2)>\cdots >μ(I^n)=(n+1)^2$都是$n$,这提供了函数$μ(I^k)$最出乎意料的行为之一.单项理想也给出了一个特殊的例子,使得$R/I^n$的Cohen-Macaulay型(或不可约指数)下降。

英文摘要:

This paper studies the numbers of minimal generators of powers of monomial ideals in polynomial rings. For a monomial ideal $I$ in two variables, Eliahou, Herzog, and Saem gave a sharp lower bound $μ(I^2)\ge 9$ for the number of minimal generators of $I^2$ with $μ(I)\geq 6$. Recently, Gasanova constructed monomial ideals such that $μ(I)>μ(I^n)$ for any positive integer $n$. In reference to them, we construct a certain class of monomial ideals such that $μ(I)>μ(I^2)>\cdots >μ(I^n)=(n+1)^2$ for any positive integer $n$, which provides one of the most unexpected behaviors of the function $μ(I^k)$. The monomial ideals also give a peculiar example such that the Cohen-Macaulay type (or the index of irreducibility) of $R/I^n$ descends.

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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