Our group works on the theory of simplification and some illustrative and relevant applications of its general ideas and concepts. Emergence of new phenomena is an important aspect of this work.
In more technical terms, we are dealing with various aspects of coarse-graining, bridging scales, irreversible dynamic systems, and nonequilibrium statistical thermodynamics.
Our favorite systems for applications range from polymeric liquids, complex fluids or soft mattter, glasses, and interfaces in multiphase systems to dissipative quantum systems and quantum field theory.
The overarching goal of all our activities is to model complex fluid behavior on different autonomous levels of description. By focusing on the essence of a problem, coarse graining provides understanding. Nonequilibrium thermodynamics is employed to establish the thermodynamic consistency of any proposed level of description ("second law" and beyond). Nonequilibrium statistical mechanics is tailored into a practical tool to relate material parameters on different levels by efficient and systematic computer simulations thus overcoming the problems associated with the existence of a wide range of time scales in complex fluids. We develop the theoretical foundations in the context of relevant systems, most importantly:
- Entangled and unentangled polymer melts.
- Glasses as nonequilibrium systems, with an emphasis on flow behavior.
- Systems with interfaces and surfaces, in which two-dimensional and three-dimensional subsystems need to be coupled consistently ("boundary thermodynamics").
- Dissipative quantum systems, including dissipative quantum field theory.
Bridging scales for the understanding of material behavior is the central theme of the Department of Materials. We support this goal both by fundamental theoretical developments (Hans Christian Öttinger) and by a variety of state-of-the-art simulation techniques (Martin Kröger).
Keywords: Boundary thermodynamics, nonequilibrium thermodynamics and statistical mechanics, coarse graining, Monte Carlo, molecular dynamics, polymer dynamics, quantum dissipation