Upper bounds on entropy production in diffusive dynamics

TL;DR

This paper derives and discusses upper bounds on entropy production rates in diffusive systems, considering various physical conditions and dynamics, with implications for understanding dissipation in nonequilibrium systems.

Contribution

The paper introduces new upper bounds on entropy production in overdamped and underdamped Langevin systems, considering non-conservative forces and temperature gradients.

Findings

Entropy production can be bounded using only driven particle statistics.

Passive degrees of freedom tend to decrease dissipation.

Temperature differences provide universal bounds on entropy production.

Abstract

Based on a variational expression for the steady-state entropy production rate in overdamped Langevin dynamics, we derive concrete upper bounds on the entropy production rate in various physical settings. For particles in a thermal environment and driven by non-conservative forces, we show that the entropy production rate can be upper bounded by considering only the statistics of the driven particles. We use this finding to argue that the presence of non-driven, passive degrees of freedom generally leads to decreased dissipation. Another upper bound can be obtained only in terms of the variance of the non-conservative force, which leads to a universal upper bound for particles that are driven by a constant force that is applied in a certain region of space. Extending our results to systems attached to multiple heat baths or with spatially varying temperature and/or mobility, we show that the temperature difference between the heat baths or the gradient of the temperature can be used to upper bound the entropy production rate. We show that most of these results extend in a straightforward way to underdamped Langevin dynamics and demonstrate them in three concrete examples.