The congruence subgroup property for the hyperelliptic modular group
The congruence subgroup property for the hyperelliptic modular group
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超椭圆模群的同余子群性质
DOI：
10.32917/hmj/1257544213
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发表时间：
2008
影响因子：
3.1
通讯作者：
M. Boggi
中科院分区：
文献类型：
--
作者：
M. Boggi
Let ${\cal M}_{g,n}$ and ${\cal H}_{g,n}$, for $2g-2+n>0$, be, respectively, the moduli stack of $n$-pointed, genus $g$ smooth curves and its closed substack consisting of hyperelliptic curves. Their topological fundamental groups can be identified, respectively, with $\Gamma_{g,n}$ and $H_{g,n}$, the so called Teichm{\"u}ller modular group and hyperelliptic modular group. A choice of base point on ${\cal H}_{g,n}$ defines a monomorphism $H_{g,n}\hookrightarrow\Gamma_{g,n}$.
Let $S_{g,n}$ be a compact Riemann surface of genus $g$ with $n$ points removed. The Teichm\"uller group $\Gamma_{g,n}$ is the group of isotopy classes of diffeomorphisms of the surface $S_{g,n}$ which preserve the orientation and a given order of the punctures. As a subgroup of $\Gamma_{g,n}$, the hyperelliptic modular group then admits a natural faithful representation $H_{g,n}\hookrightarrow\operatorname{Out}(\pi_1(S_{g,n}))$.
The congruence subgroup problem for $H_{g,n}$ asks whether, for any given finite index subgroup $H^\lambda$ of $H_{g,n}$, there exists a finite index characteristic subgroup $K$ of $\pi_1(S_{g,n})$ such that the kernel of the induced representation $H_{g,n}\to\operatorname{Out}(\pi_1(S_{g,n})/K)$ is contained in $H^\lambda$. The main result of the paper is an affirmative answer to this question for $n\geq 1$.
Let ${\cal M}_{g,n}$ and ${\cal H}_{g,n}$, for $2g-2+n>0$, be, respectively, the moduli stack of $n$-pointed, genus $g$ smooth curves and its closed substack consisting of hyperelliptic curves. Their topological fundamental groups can be identified, respectively, with $\Gamma_{g,n}$ and $H_{g,n}$, the so called Teichm{\"u}ller modular group and hyperelliptic modular group. A choice of base point on ${\cal H}_{g,n}$ defines a monomorphism $H_{g,n}\hookrightarrow\Gamma_{g,n}$.
Let $S_{g,n}$ be a compact Riemann surface of genus $g$ with $n$ points removed. The Teichm\"uller group $\Gamma_{g,n}$ is the group of isotopy classes of diffeomorphisms of the surface $S_{g,n}$ which preserve the orientation and a given order of the punctures. As a subgroup of $\Gamma_{g,n}$, the hyperelliptic modular group then admits a natural faithful representation $H_{g,n}\hookrightarrow\operatorname{Out}(\pi_1(S_{g,n}))$.
The congruence subgroup problem for $H_{g,n}$ asks whether, for any given finite index subgroup $H^\lambda$ of $H_{g,n}$, there exists a finite index characteristic subgroup $K$ of $\pi_1(S_{g,n})$ such that the kernel of the induced representation $H_{g,n}\to\operatorname{Out}(\pi_1(S_{g,n})/K)$ is contained in $H^\lambda$. The main result of the paper is an affirmative answer to this question for $n\geq 1$.
DOI：
--
发表时间：
2008
期刊：
J. Math. Kyoto Univ. 47
影响因子：
--
作者：
Eyral;C;Oka;M.;倉田 俊彦;R.Kobayashi;A.Hiraki and J.Koolen;望月新一
通讯作者：
望月新一