Model atomic systems in intense laser fields: Exact time-dependent density functional and Floquet theory

The ab initio solution of the time-dependent Schrödinger equation for a many-body system is feasible for only a few constituents. Success of TDDFT when it comes to highly correlated electron dynamics is very limited. In this thesis, the exact exchange-correlation potential for the highly correlated process of autoionization is constructed. One may try to employ the time-periodicity of external drivers. If this could also be applied to the time-dependent Kohn-Sham equation the time-dependent many-body problem could be reduced to a time-independent one. It is investigated if this is possible