We address two questions of Simon Thomas. First, we show that for any n >= 3 one can find a four-generated free subgroup of SLn (Z) which is profinitely dense. More generally, we show that an arithmetic group Gamma that admits the congruence subgroup prope ...
We survey the mixing patterns which can be derived from the discrete groups Sigma(36 x 3), Sigma( 72 x 3), Sigma(216 x 3) and Sigma(360 x 3), if these are broken to Abelian subgroups G(e) and G(nu) in the charged lepton and neutrino sector, respectively. S ...
The special linear group G = SLn(Z[x(1), ... , x(k)]) (n at least 3 and k finite) is called the universal lattice. Let n be at least 4, and p be any real number in (1, infinity). The main result is the following: any finite index subgroup of G has the fixe ...
We study (connected) reductive subgroups G of a reductive algebraic group H, where G contains a regular unipotent element of H. The main result states that G cannot lie in a proper parabolic subgroup of H. This result is new even in the classical case H = ...