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arXiv · 2603.09850

Non-equilibrium generalized Langevin equation for multi-dimensional observables

Benjamin J. A. Héry·Lucas Tepper·Andrea Guljas·Artem Pavlov·Beate Koksch·Cecilia Clementi·Roland R. Netz
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Abstract

The Mori-Zwanzig formalism is a powerful theoretical framework for deriving equations of motion for coarse-grained observables in the form of generalized Langevin equations (GLEs) involving evolution and projection operators. Using a time-dependent many-body Hamiltonian and a multi-dimensional Mori projection operator, we derive a non-equilibrium Mori GLE for a multi-dimensional observable of interest $\vec{A}$ that consists of a Markovian force, a running integral over time of a non-Markovian friction force, and an orthogonal force that is often interpreted as a random force. We study the structure of the derived GLE in three limiting cases: when the components of $\vec{A}$ are uncorrelated, when the Hamiltonian is time-independent and thus the system is at equilibrium, and when both conditions are simultaneously satisfied. We highlight the presence of a contribution to the Markovian force that takes the form of an instantaneous friction force which only vanishes when the components of $\vec{A}$ are uncorrelated. Our non-Markovian framework is an important step towards the systematic modeling of the coupled kinetics of coarse-grained reaction coordinates in biological complex systems, exemplified for the coupled intra- and inter-protein folding during fibril formation of the human islet amyloid polypeptide (IAPP).

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Benjamin J. A. Héry, Lucas Tepper, Andrea Guljas, Artem Pavlov, Beate Koksch, Cecilia Clementi, Roland R. Netz. 2026-03-10. Non-equilibrium generalized Langevin equation for multi-dimensional observables. https://arxiv.org/abs/2603.09850

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