Kai-Uwe Bux

  1. The congruence subgroup property for $Aut F_2$: A group-theoretic proof of Asada's theorem.

    Authors: Mikhail Ershov, Kai-Uwe Bux, Andrei Rapinchuk
    Subjects: Group Theory
    Abstract

    The goal of this paper is to give a group-theoretic proof of the congruence
    subgroup property for $Aut(F_2)$, the group of automorphisms of a free group on
    two generators. This result was first proved by Asada using techniques from
    anabelian geometry, and our proof is, to a large extent, a translation of
    Asada's proof into group-theoretic language. This translation enables us to
    simplify many parts of Asada's original argument and prove a quantitative
    version of the congruence subgroup property for $Aut(F_2)$.

  2. Finiteness Properties of Chevalley Groups over a Polynomial Rings over a Finite Field.

    Authors: Kai-Uwe Bux, Ralf Gramlich, Stefan Witzel
    Subjects: Group Theory
    Abstract

    It is known from work by H. Abels and P. Abramenko that for a classical
    Fq-group G of rank n the arithemetic lattice G(Fq[t]) of Fq[t]-rational points
    is of type Fn-1 provided that q is large enough. We show that the statement is
    true without any assumption on q and for any isotropic, absolutely almost
    simple group G defined over Fq.

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