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arXiv 2409.09384math.AG
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关于加权齐次奇点的第k个Tjurina数

On the $k$-th Tjurina number of weighted homogeneous singularities

Sun Yat-Sen University(中山大学);Beijing Institute of Mathematical Sciences and Applications(北京国际数学研究中心);Tsinghua University(清华大学)

Chuangqiang Hu, Stephen S. -T. Yau, Huaiqing Zuo

AI总结:

本文提出一种新的复形计算加权齐次奇点的第k个Tjurina数的方法,并给出了通用公式。

摘要:

设(X,0)是一个由加权齐次多项式f定义的孤立奇点。令O表示在原点处的全纯函数germ的局部代数,其极大理想为m。我们研究第k个Tjurina代数,定义为A_k(f):=O/(f, m^k J(f)),其中J(f)表示f的雅可比理想。零阶Tjurina代数已知代表半通用变形(X,0)基础空间的切空间。受此观察启发,我们探讨相对于固定k余点的(X,0)的变形。我们证明相应的变形函数的切空间是第k个Tjurina代数的子空间。显式计算第k个Tjurina数,即第k个Tjurina代数的维数,在理解这些变形中起关键作用。根据Milnor和Orlik的结果,零阶Tjurina数可以明确地用f中变量的权重表示。然而,我们观察到当k超过X的乘数时,第k个Tjurina数变得更加复杂,并不单由变量的权重决定。在本文中,我们引入了一个源自经典Koszul复形的新复形,并为所有k≥0获得一个可计算的第k个Tjurina数公式。作为应用,我们计算了所有三变量加权齐次奇点的第k个Tjurina数。

英文摘要:

Let $ (X,0) $ denote an isolated singularity defined by a weighted homogeneous polynomial $ f $. Let $ \mathcal{O}$ be the local algebra of holomorphic function germs at the origin, with the maximal ideal $m $. We study the $k$-th Tjurina algebra, defined by $ A_k(f): = \mathcal{O} / \left( f , m^k J(f) \right) $, where $J(f)$ denotes the Jacobian ideal of $ f $. The zeroth Tjurina algebra is well known to represent the tangent space of the base space of the semi-universal deformation of $(X, 0)$. Motivated by this observation, we explore the deformation of $(X,0)$ with respect to a fixed $k$-residue point. We show that the tangent space of the corresponding deformation functor is a subspace of the $k$-th Tjurina algebra. Explicit calculation of the $k$-th Tjurina numbers, which correspond to the dimensions of the $k$-th Tjurina algebras, plays a crucial role in understanding these deformations. According to the results of Milnor and Orlik, the zeroth Tjurina number can be expressed explicitly in terms of the weights of the variables in $f$. However, we observe that for values of $k$ exceeding the multiplicity of $X$, the $k$-th Tjurina number becomes more intricate and is not solely determined by the weights of the variables. In this paper, we introduce a novel complex derived from the classical Koszul complex and obtain a computable formula for the $k$-th Tjurina numbers for all $ k \geqslant 0 $. As an application, we calculate the $k$-th Tjurina numbers for all weighted homogeneous singularities in three variables.

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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