Marc-Thomas Russo

The derivation of thermodynamics from microscopic dynamics has been one of the fundamental problems that physicists have faced for almost a century. Since the celebrated work of Boltzmann, thermodynamics, and in particular the law of entropy increase, is thought of as a macroscopic theory descending from statistical mechanics postulates. Despite Boltzmann’s approach being the recognized gold standard needed to explain the emergence of macroscopic irreversibility, questions still remain open on how to link this with dynamics that are microscopically reversible. The equations of motion governing Hamiltonian systems are time-reversal invariant, both classically and quantum mechanically, and do not account for a microscopic arrow of time. In this project we aim to tackle this issue within an open quantum systems approach and assess the current understanding of the emergence of dissipation and irreversibility out of a fully dynamical and Hamiltonian picture. In particular we will analyse some of the reduction procedures adopted in this framework and establish their equivalence to Boltzmann coarse-graining approaches both in phase space and in time. We will focus on systems that are characterized by both Markovian and non-Markovian effective dynamics and establish a connection between different microscopic dynamics and macroscopic irreversibility. The overarching scope of the work is to identify and formalize any dynamical element that breaks the time-reversal invariance of microscopic theories. The project is part of a larger programme of research conducted at Surrey to investigate, from first principles, the dynamics of quantum systems in interaction with their surroundings, and the emergence of macroscopic irreversibility and the arrow of time.