Foundation of statistical mechanics under even more experimentally realistic conditions

TL;DR

This paper extends rigorous quantum thermalization results from sudden quenches to finite-time perturbations, showing that systems still equilibrate if they involve many energy levels, thus making the theory more physically realistic.

Contribution

It generalizes existing quantum equilibration theorems to include finite-time quenches, addressing more realistic dynamical conditions.

Findings

Finite-time quenches still lead to equilibration under certain conditions.

Equilibration occurs if the system populates many energy levels.

Mathematical proofs are more complex but support the same physical conclusion.

Abstract

Understanding how macroscopic systems exhibit irreversible thermal behavior has been a long-standing challenge, first brought to prominence by Boltzmann. Recent advances have established rigorous conditions for isolated quantum systems to equilibrate to a maximum entropy state, contingent upon weak assumptions. These theorems, while powerful, apply for a sudden quench. However, natural processes involve finite-time perturbations or quenches, which raises a crucial question: Can these systems still equilibrate under more realistic, finite-time dynamics? In this work, we extend the established results to account for finite-time quenches, demonstrating that even under finite-time perturbations, the system will equilibrate provided it populates many significant energy levels. While the mathematical proof is more intricate than in the instantaneous case, the physical conclusion remains the same: sufficient perturbation leads to equilibration. Our results provide a broader and more physically realistic framework for understanding thermalization in isolated quantum systems