\chapter*{Acknowledgment}
\addcontentsline{toc}{chapter}{Acknowledgment}

First of all, I would like to thank Prof. Dr. Bernd Stritzker and Prof. Dr. Kai Nordlund for accepting me as a PhD student at their chairs at the University of Augsburg and Helsinki.
Although Mr. Stritzker is doing experimental physics in Augsburg he gave me the opportunity to do this more or less theoretical work.
During my stays in Finland Mr. Nordlund \ldots

