The theory group deals with several interrelated areas of physics. The main interest is to explain observations and find proper descriptions of quantum phenomena in (mainly in the condensed matter) systems, which are out of equilibrium. Many aspects of non-equilibrium dynamics are still poorly understood and represent continuous challenges both for theoretical as well as experimental studies. The aim of the efforts of the group is thus a better understanding of quantum phenomena, generally far from equilibrium, like transients or steady state transport, their dependence on initial conditions, time dependent external fields, interactions, and details of studied systems. Systems studied are bulk systems as well as small systems of nanoscopic sizes and various dimensions. To reach this goal the members of the group combine knowledge and methods from thermodynamics, linear response theory, non-equilibrium statistical physics, quantum many body theory, foundations of quantum mechanics and quantum field theory. They use various forms and combinations of linear response formalism, density matrix and Non-equilibrium Green’s function techniques. Special care is taking of developing and testing approximations which are suited for the descriptions of open systems and their interaction with reservoirs. Experiences from all the above areas are used also in our studies of biological systems as well as thermal properties of matter.