Analytical Theory and Models

The goal of the theory efforts on model systems is to make rigorous and well controlled statements about generic and universal properties of strongly interacting or strongly disordered quantum many-body systems. As a role, such systems cannot be captured using first principles approaches. However the low-energy and long wavelength properties can be described in terms of model Hamiltonians that allow for generic, often model-independent nsights. Examples are unconventional superconductors, Josephson junction arrays, quantum magnets, quantum wires, carbon nanotubes and graphene, or topologically nontrivial system. Key challenges are the theoretical description of Coulomb correlations, the proper treatment of quantum interference phenomena in disordered systems, the role of quantum phase transitions and quantum criticality in nanostructures and bulk, the physics of decoherence, or the adequate analysis of nonequilibrium phenomena. These exciting problems are being addressed using  computational methods and analytic quantum field theoretic tools, with close interaction with experiment and other theoretic approaches.