Dresden 2026 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 9: Statistical Physics far from Thermal Equilibrium I

DY 9.5: Vortrag

Montag, 9. März 2026, 10:30–10:45, ZEU/0160

Thermophoresis of a tracer particle via coarse graining of an explicit nonequilibrium medium — •Wade Hodson and Aljaz Godec — Mathematical Physics and Stochastic Dynamics, Institute of Physics, University of Freiburg

We investigate the transport of a tracer particle embedded in an explicitly represented medium with a position-dependent temperature. The medium consists of a chain of harmonic oscillators, in which a temperature gradient is established by connecting each particle to its own heat reservoir. We then couple a tracer to this medium via a generic potential. Under these conditions, we find that the tracer preferentially diffuses in one direction due to the temperature gradient, a phenomenon known as thermophoresis. We study the model analytically in various regimes, including the weak coupling, low temperature, overdamped, Markovian, and hydrodynamic limits, and supplement these results with numerical computations. In the Markovian limit, we are able to coarse-grain over the medium's degrees of freedom to obtain a Langevin equation for the tracer, with a potential of mean force, a damping coefficient, and a diffusion coefficient which can be evaluated in the low-temperature regime. We focus on the analysis of this low-temperature Langevin equation, with a particular interest in the parameter regimes where the tracer can potentially exhibit negative thermophoresis, in which the tracer diffuses preferentially towards higher temperatures. Finally, we generalize our results to higher dimensions, by coupling the tracer to a two- or three-dimensional medium.

Keywords: thermophoresis; thermodiffusion; coarse-graining; temperature gradient; nonequilibrium bath