arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 2108.03261math.NTmath.GR
收藏

Drinfeld模群的拟内自同构

Quasi-inner automorphisms of Drinfeld modular groups

A. W. Mason, Andreas Schweizer

AI总结:

该研究定义了Drinfeld模群$GL_2(A)$的拟内自同构群$Quinn(G)$,证明其同构于理想类群的2-挠子群,并揭示了它在尖点、椭圆点及Bruhat-Tits树商图的端上的作用性质,推广了Serre的相关结果。

摘要:

设$A$是有限域${\mathbb F}_q$上的代数函数域$K$中在固定位$\infty$之外整的元素构成的集合。令$G=GL_2(A)$为一个Drinfeld模群。$G$在$GL_2(K)$(其中$K$是$A$的商域)中的正规化子诱导出$G$的自同构,我们称之为“拟内自同构”。模掉$G$的内自同构后,它们构成群$Quinn(G)$,该群同构于理想类群${\mathrm Cl}(A)$中的2-挠子群${\mathrm Cl}(A)_2$。\n 群$Quinn(G)$作用在所有与$G$相关的对象上。例如,它自由作用在$G$的尖点和椭圆点上。若${\mathcal T}$是相伴的Bruhat-Tits树,则$Quinn(G)$的元素诱导出商图$G\setminus{\mathcal T}$的非平凡自同构,推广了Serre的早期结果。已知$G\setminus{\mathcal T}$的端与$G$的尖点一一对应,因此$Quinn(G)$在这些端上自由作用。此外,$Quinn(G)$在那些与稳定子群同构于$GL_2({\mathbb F}_q)$的$G\setminus{\mathcal T}$顶点一一对应的端上传递作用。

英文摘要:

Let $A$ be the set of elements in an algebraic function field $K$ over ${\mathbb F}_q$ which are integral outside a fixed place $\infty$. Let $G=GL_2(A)$ be a {\it Drinfeld modular group}. The normalizer of $G$ in $GL_2(K)$, where $K$ is the quotient field of $A$, gives rise to automorphisms of $G$, which we refer to as {\it quasi-inner}. Modulo the inner automorphisms of $G$ they form a group $Quinn(G)$ which is isomorphic to ${\mathrm Cl}(A)_2$, the $2$-torsion in the ideal class group ${\mathrm Cl}(A)$. The group $Quinn(G)$ acts on all kinds of objects associated with $G$. For example, it acts freely on the cusps and elliptic points of $G$. If ${\mathcal T}$ is the associated Bruhat-Tits tree the elements of $Quinn(G)$ induce non-trivial automorphisms of the quotient graph $G\setminus{\mathcal T}$, generalizing an earlier result of Serre. It is known that the ends of $G\setminus{\mathcal T}$ are in one-one correspondence with the cusps of $G$. Consequently $Quinn(G)$ acts freely on the ends. In addition $Quinn(G)$ acts transitively on those ends which are in one-one correspondence with the vertices of $G\setminus{\mathcal T}$ whose stabilizers are isomorphic to $GL_2({\mathbb F}_q)$.

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。

↑