Regensburg 2019 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 55: Poster: Noneq. Stat. Phys., Stat. Bio. Phys., Brownian

DY 55.14: Poster

Thursday, April 4, 2019, 15:00–18:00, Poster B2

Nonlinear response theory in classical systems — •Fenna Müller and Matthias Krüger — Institut für Theoretische Physik, Friedrich-Hund-Platz 1, 37077 Göttingen

The fluctuation-dissipation theorem describes the linear response of a system in relation to equilibrium fluctuations. However, there is no corresponding general theorem or scheme to do the same for the nonlinear response. Here, we develop a coarse grained scheme for computation of nonlinear responses based on path integrals [2]. Comparing the time reversed system to its original, one can identify several components, such as entropy flux in the first order, as done e.g. in [1]. In experiments it is oftentimes impossible or impractical to observe the whole system with all its microstates, however. Therefore, we extend the path integral formalism to include a coarse graining, see [2]. All response formula describe the system in terms of coarse grained variables and direct access to microscopic variables is not necessary. We explore using this method for time dependent pertubations by applying it to the analytically solvable two state model.

[1] Basu, U., Krüger, M., Lazarescu, A., & Maes, C. (2015). Frenetic aspects of second order response. Physical Chemistry Chemical Physics, 17(9), 6653-6666. [2] Basu, U., Helden, L., & Krüger, M. (2018). Extrapolation to Nonequilibrium from Coarse-Grained Response Theory. Physical review letters, 120(18), 180604.