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arXiv 1309.4698math.ACmath.RA
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Koszul行列式环与线性型的$2\times e$矩阵

Koszul determinantal rings and $2\times e$ matrices of linear forms

Hop D. Nguyen, Phong Dinh Thieu, Thanh Vu

摘要:

设$k$是特征$0$的代数闭域.设$X$是多项式环$k[\mathsf{x}_1, \ldots,\mathsf{x}_n]$上的线性型的$2\times e$矩阵(其中$e,n\ge 1$)。证明了行列式环$R = k[\mathsf{x}_1,\ldots,\mathsf{x}_n]/I_2(X)$是Koszul当且仅当在$X$的Kronecker-Weierstrass标准型中,幂零块的最大长度至多是涡卷块的最小长度的两倍.作为应用,我们对所有截面环的自然坐标都是Koszul的有理正规涡卷进行了分类。这一结果解决了一个猜想由于孔卡。

英文摘要:

Let $k$ be an algebraically closed field of characteristic $0$. Let $X$ be a $2\times e$ matrix of linear forms over a polynomial ring $k[\mathsf{x}_1, \ldots,\mathsf{x}_n]$ (where $e,n\ge 1$). We prove that the determinantal ring $R = k[\mathsf{x}_1,\ldots,\mathsf{x}_n]/I_2(X)$ is Koszul if and only if in the Kronecker-Weierstrass normal form of $X$, the largest length of a nilpotent block is at most twice the smallest length of a scroll block. As an application, we classify rational normal scrolls whose all section rings by natural coordinates are Koszul. This result settles a conjecture due to Conca.

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