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arXiv 2210.02481math.GRmath.GTmath.NT
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PSL(2, K)中的共轭类

Conjugacy classes in PSL(2, K)

Christopher-Lloyd Simon

AI总结:

本文研究PSL(2, K)在二次形式上的共轭类划分及其几何解释,结合Hilbert符号和模算术轨道的几何特性。

摘要:

我们首先在特征不为2的域K上描述了PGL(2, K)和PSL(2, K)的adjoint作用在其李代数sl(2, K)上的轨道。虽然前者是众所周知的,但后者导致了解一般的Pell-Fermat方程,这些方程刻画了相应的轨道。合成方法使我们能够改变基域,我们通过具有三个和五个元素的域来说明这一图景,并与四面体群和二十面体群的几何相关联。尽管结果可能看起来熟悉,但现有文献似乎没有以如此一般或详细的方式涵盖这些结果。我们应用这一讨论将PSL(2, Z)的整数二元二次型类划分成PSL(2, K)的类。当K=C时,我们得到给定判别式的类群。然后我们以Hilbert符号完全描述了它们在PSL(2, Q)类中的划分,并将其与种群划分相关联。这些结果是经典的,但我们的几何方法具有独立的兴趣,因为它可能为Gauss组合的几何提供新的见解,并统一了函数域上的图景。最后,我们为模算术轨道PSL(2, Z) \ H提供了一个几何解释,解释了当两个点或两个闭合测地线对应于PSL(2, K)等价的二次形式时,如何用双曲距离和这些模算术循环之间的角度来解释。这些几何量与模算术结的链接数有关。它们的分布性质可以用二次晶格(sl(2, Z),det)的几何来研究,但此类研究在此未被深入探讨。

英文摘要:

We first describe, over a field K of characteristic different from 2, the orbits for the adjoint actions of the Lie groups PGL(2, K) and PSL(2, K) on their Lie algebra sl(2, K). While the former are well known, the latter lead to the resolution of generalised Pell-Fermat equations which characterise the corresponding orbit. The synthetic approach enables to change the base field, and we illustrate this picture over the fields with three and five elements, in relation with the geometry of the tetrahedral and icosahedral groups. While the results may appear familiar, they do not seem to be covered in such generality or detail by the existing literature. We apply this discussion to partition the set of PSL(2, Z)-classes of integral binary quadratic forms into groups of PSL(2, K)-classes. When K = C we obtain the class groups of a given discriminant. Then we provide a complete description of their partition into PSL(2, Q)-classes in terms of Hilbert symbols, and relate this to the partition into genera. The results are classical, but our geometrical approach is of independent interest as it may yield new insights into the geometry of Gauss composition, and unify the picture over function fields. Finally we provide a geometric interpretation in the modular orbifold PSL(2, Z) \ H for when two points or two closed geodesics correspond to PSL(2, K)-equivalent quadratic forms, in terms of hyperbolic distances and angles between those modular cycles. These geometric quantities are related to linking numbers of modular knots. Their distribution properties could be studied using the geometry of the quadratic lattice (sl(2, Z), det) but such investigations are not pursued here.

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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