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arXiv 2201.05713math.AG
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具有固定伴随分次的非常一般混合Hodge结构的Mumford-Tate群的幂幺根

The unipotent radical of the Mumford-Tate group of a very general mixed Hodge structure with a fixed associated graded

Payman Eskandari, V. Kumar Murty

摘要:

给定有理向量空间$M_\mathbb{Q}$上具有固定权滤子$W_\cdot$和固定关联分次Hodge结构$Gr^WM$的所有混合Hodge结构族自然地与复仿射空间一一对应。研究了非常一般的Mumford-Tate群的幂幺根.我们这样做,通过使用一般的Tannakian结果,涉及幂幺根的基本群的一个对象在过滤Tannakian范畴的扩展类的对象来自过滤。我们的主要结果是:如果$Gr^WM$是可极化的,并且满足一定的条件,那么在参数化仿射空间的可数个真Zerkki闭子集的并之外,族中对象的Mumford-Tate群的幂幺根等于$M_\mathbb{Q}$上与权滤子相关的$GL(M_\mathbb{Q})$的抛物子群的幂幺根(换句话说,在可数个真Zebriki闭集的并之外,Mumford-Tate群的幂幺根幂幺根是人们所希望的那样大)。请注意,这里$Gr^WM$本身可能有一个小的Mumford-Tate群组。

英文摘要:

The family of all mixed Hodge structures on a given rational vector space $M_\mathbb{Q}$ with a fixed weight filtration $W_\cdot$ and a fixed associated graded Hodge structure $Gr^WM$ is naturally in a one to one correspondence with a complex affine space. We study the unipotent radical of the very general Mumford-Tate group of the family. We do this by using general Tannakian results which relate the unipotent radical of the fundamental group of an object in a filtered Tannakian category to the extension classes of the object coming from the filtration. Our main result shows that if $Gr^WM$ is polarizable and satisfies some conditions, then outside a union of countably many proper Zariski closed subsets of the parametrizing affine space, the unipotent radical of the Mumford-Tate group of the objects in the family is equal to the unipotent radical of the parabolic subgroup of $GL(M_\mathbb{Q})$ associated to the weight filtration on $M_\mathbb{Q}$ (in other words, outside a union of countably many proper Zariski closed sets the unipotent radical of the Mumford-Tate group is as large as one may hope for it to be). Note that here $Gr^WM$ itself may have a small Mumford-Tate group.

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