O. Politano | Searcharxiv

arXiv2026

Temporal reversibility of a fluid mixture under concentration gradient

A binary fluid mixture in contact with lateral particle reservoirs is considered. By imposing different particle concentrations in these reservoirs, the system can be maintained under controlled non-equilibrium conditions. Previous stochastic approaches have revealed an unexpected property of the system's state trajectory, namely that it remains time-reversible even when the system is driven out of equilibrium. In the absence of relevant experimental evidence, we employ microscopic molecular dynamics simulations to assess the validity of this surprising result. Remarkably, the simulation results unambiguously confirm the prediction of the stochastic analysis.

cond-mat.stat-mech↗

arXiv2024

Temporal reversibility of reactive systems out of equilibrium: Molecular dynamics simulation

The second law of thermodynamics states that entropy production in macroscopic systems is non-negative, reaching zero only at thermodynamic equilibrium. As a corollary, this implies that the state trajectory of macroscopic systems is inherently time-irreversible under out-of-equilibrium conditions. However, over the past half-century, various studies have shown that this principle does not universally apply to the composition sample paths of certain isothermal reactive systems. Theoretical frameworks leading to this surprising observation primarily focus on perfectly homogeneous systems (often referred to as zero-dimensional systems), which inherently exclude the effects of local fluctuations. This oversimplification may account for the paradoxical theoretical predictions. In the absence of relevant experimental data, this paper seeks to explore this phenomenon through microscopic simulations.

cond-mat.stat-mech↗