Theoretical physics of quantum many-body systems. Strongly correlated fermionic (electronic) systems as well bosonic systems and Bose-Einstein condensates (BECs), i.e., ultracold atomic gases and photonic BECs. Specifically, time-resolved nonequilibrium dynamics of these systems. Quantum entanglement, coherence and dephasing in open quantum systems coupled to a reservoir. Method development: Semianalytic methods: Feynman- diagram techniques far from equilibrium and numerical solution of nonlinear integrodifferential equations, renormalization group methods. PI in the ML4Q cluster and in SFB185 OSCAR.