Brownian Particles in Nonequilibrium Solvents
by Boris Müller
Date of Examination:2019-12-10
Date of issue:2020-01-08
Advisor:Prof. Dr. Matthias Krüger
Referee:Prof. Dr. Matthias Krüger
Referee:Prof. Dr. Marcus Müller
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Abstract
English
Colloidal particles suspended in purely viscous (Newtonian) solvents have played a crucial role in understanding nonequilibrium processes and in the development of statistical physics out of equilibrium. The theoretical description of these systems usually rests on the assumption of a clear separation of time scales between the slow dynamical variables of probe particles and the fast dynamical variables of molecular solvent particles. In recent years, viscoelastic fluids have entered the limelight of both theory and experiment. Most importantly, they are characterized by large structural relaxation times that can be comparable to or even larger than those of colloidal motion. The reason for the slow relaxation of these fluids lies in their complex microstructure that allows for the storage and dissipation of energy. These fluids comprise a huge variety of systems such as biological fluids, semi-dilute polymer solutions, micellar systems, or dense colloidal suspensions. In this thesis, we thoroughly investigate and extend the theory of Brownian motion in complex fluids in and out of equilibrium.
Keywords: Brownian motion; Viscoelastic solvents; Projection operator formalism; Microrheology; Nonlinear Langevin equation; Stochastic Prandtl-Tomlinson model; Negative memory modes; Nonlinear response theory; Colloidal particles; Path integral formalism; Linearization techniques