Irreducibly acting subgroups of $Gl(n,\rr)$
arXiv:math/0507047
Abstract
In this note we prove the following three algebraic facts which have applications in the theory of holonomy groups and homogeneous spaces: Any irreducibly acting connected subgroup $G \subset Gl(n,\rr)$ is closed. Moreover, if admits an invariant bilinear form of Lorentzian signature, is maximal, i.e. it is conjugated to . Finally we calculate the vector space of -invariant symmetric bilinear forms, show that it is at most 3-dimensional, and determine the maximal stabilizers for each dimension.
21 pages