Brigitte E. Breckner, Boku Wien (Koautor: Wolfgang A.F. Ruppert)
This talk presents a short survey over some recent results connected with orders on a Lie group . One of the central tasks in this context is to find conditions under which order intervals are compact, so that, e.g., Volterra kernels can be defined. We define and describe the set of alien elements in the semigroup of elements as a kind of ``obstruction'' to compactness of order intervals. In particular, we give explicit results in the case of .