| Issue |
EPL
Volume 154, Number 5, June 2026
|
|
|---|---|---|
| Article Number | 57001 | |
| Number of page(s) | 6 | |
| Section | Biological and soft matter physics | |
| DOI | https://doi.org/10.1209/0295-5075/ae66b4 | |
| Published online | 18 May 2026 | |
Snap, crackle, and pop: This is why the potential of mean force clashes with the fluctuation dissipation relation
Institut für Physik, Albert-Ludwigs-Universität Freiburg - Hermann-Herder-Straße 3, 79104 Freiburg im Breisgau, Germany
Received: 17 November 2025
Accepted: 29 April 2026
Abstract
We analyze the non-linear generalized Langevin equation which contains a thermodynamic force. Our method bypasses the projection-operator formalism. We show that even for systems in thermal equilibrium the presence of the thermodynamic force implies that the auto-correlation function of the fluctuating force becomes non-stationary. We further illustrate that a standard coarse-graining procedure that neglects this fact predicts waiting-time distributions incompatible with the original, microscopic process. We conclude that one needs to proceed with care when adding thermodynamic driving forces to the Langevin equation.
© 2026 The author(s)
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