论文标题
免费组的无凝结抛物线字符$ f_2 $:超级组密度和尼尔森班级的riley slice中的nielsen类
Nondiscrete parabolic characters of the free group $F_2$: supergroup density and Nielsen classes in the complement of the Riley slice
论文作者
论文摘要
免费组$ f_2 $的抛物线表示是两个发电机的图像是$ psl(2,\ ic)$的抛物线元素。 Riley Slice是一个封闭的子集$ {\ cal r} \ subset \ ic $,是$ f_2 $的抛物线,离散和忠实字符的模型。 Riley Slice的补充是一个有界的Jordan域,其中存在孤立的点,仅在边界积累,对应于$ PSL(2,\ IC)$的僵化子组的抛物线离散和忠实表示。 Aimi,Akiyoshi,Lee,Oshika,Parker,Lee,Sakai,Sakuma \&Yoshida的最新工作在拓扑上确定了所有这些群体。在这里,我们给出了非核代表的第一个确定的实质性特性,并证明了超组密度定理:给定任何不可约束的抛物线代表$ρ_*:f_2 \:f_2 \ to psl(2,\ ic)$ with with with with with with with with with with with with with with with with with with with with with with with with with with with with with with with with with with with with with nont-discrete proccrete $ρ_0$ρ_2$ρ_2 $ρ_*(F_2)$的共轭作为适当的子组。 This implies that if $Γ_*$ is any nonelementary group generated by two parabolic elements (discrete or otherwise) and $γ_0$ is any point in the complement of the Riley slice, then in any neighbourhood of $γ$ there is a point corresponding to a nonelementary group generated by two parabolics with a conjugate of $Γ_*$ as a proper subgroup.然后,使用这些想法,我们表明存在非核心抛物线表示,并任意大量的尼尔森类别类别的抛物线发电机类别。
A parabolic representation of the free group $F_2$ is one in which the images of both generators are parabolic elements of $PSL(2,\IC)$. The Riley slice is a closed subset ${\cal R}\subset \IC$ which is a model for the parabolic, discrete and faithful characters of $F_2$. The complement of the Riley slice is a bounded Jordan domain within which there are isolated points, accumulating only at the boundary, corresponding to parabolic discrete and faithful representations of rigid subgroups of $PSL(2,\IC)$. Recent work of Aimi, Akiyoshi, Lee, Oshika, Parker, Lee, Sakai, Sakuma \& Yoshida, have topologically identified all these groups. Here we give the first identified substantive properties of the nondiscrete representations and prove a supergroup density theorem: given any irreducible parabolic representation $ρ_*:F_2\to PSL(2,\IC)$ whatsoever, any non-discrete parabolic representation $ρ_0$ has an arbitrarily small perturbation $ρ_ε$ so that $ρ_ε(F_2)$ contains a conjugate of $ρ_*(F_2)$ as a proper subgroup. This implies that if $Γ_*$ is any nonelementary group generated by two parabolic elements (discrete or otherwise) and $γ_0$ is any point in the complement of the Riley slice, then in any neighbourhood of $γ$ there is a point corresponding to a nonelementary group generated by two parabolics with a conjugate of $Γ_*$ as a proper subgroup. Using these ideas we then show that there are nondiscrete parabolic representations with an arbitrarily large number of distinct Nielsen classes of parabolic generators.