Dresden 2026 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 54: Statistical Physics: General II

DY 54.9: Talk

Thursday, March 12, 2026, 17:15–17:30, ZEU/0114

Predicting Friction Modifications under Harmonic Confinement via Perturbative Mori Projections — •Felix Riesterer and Roland Netz — Department of Physics, Freie Universität Berlin, Germany

Previous studies have shown that external potentials can alter friction, yet a comprehensive theoretical explanation for this effect is still lacking. This issue is particularly relevant for enhanced sampling techniques, such as umbrella sampling, where applied biases can distort dynamical observables.

We present a theoretical framework based on perturbative projections within the Mori Generalized Langevin Equation (GLE). The approach provides an explicit first-order prediction of the friction correction due to an external potential using only unbiased simulations. Furthermore, it clarifies the conditions under which such corrections arise.

To validate the theory, we perform molecular dynamics simulations of a Lennard-Jones fluid (argon) confined in a harmonic potential of varying strength. The theoretical predictions capture the friction enhancement to first order in the potential stiffness. These results demonstrate how harmonic umbrella sampling can modify friction, highlighting the potential impact on the interpretation of dynamical quantities obtained from biased simulations.

Keywords: Generalized Langevin Equation; Molecular dynamics; Umbrella sampling; Projection operator formalism; Molecular friction