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Open AccessArticle

On Work and Heat in Time-Dependent Strong Coupling

by Erik Aurell 1,2
KTH—Royal Institute of Technology, AlbaNova University Center, SE-106 91 Stockholm, Sweden
Departments of Computer Science and Applied Physics, Aalto University, FIN-00076 Aalto, Finland
Entropy 2017, 19(11), 595;
Received: 18 August 2017 / Revised: 14 September 2017 / Accepted: 28 October 2017 / Published: 7 November 2017
(This article belongs to the Special Issue Thermodynamics and Statistical Mechanics of Small Systems)
This paper revisits the classical problem of representing a thermal bath interacting with a system as a large collection of harmonic oscillators initially in thermal equilibrium. As is well known, the system then obeys an equation, which in the bulk and in the suitable limit tends to the Kramers–Langevin equation of physical kinetics. I consider time-dependent system-bath coupling and show that this leads to an additional harmonic force acting on the system. When the coupling is switched on and switched off rapidly, the force has delta-function support at the initial and final time. I further show that the work and heat functionals as recently defined in stochastic thermodynamics at strong coupling contain additional terms depending on the time derivative of the system-bath coupling. I discuss these terms and show that while they can be very large if the system-bath coupling changes quickly, they only give a finite contribution to the work that enters in Jarzynski’s equality. I also discuss that these corrections to standard work and heat functionals provide an explanation for non-standard terms in the change of the von Neumann entropy of a quantum bath interacting with a quantum system found in an earlier contribution (Aurell and Eichhorn, 2015). View Full-Text
Keywords: stochastic thermodynamics; strong coupling; Zwanzig model; quantum-classical correspondence for heat stochastic thermodynamics; strong coupling; Zwanzig model; quantum-classical correspondence for heat
MDPI and ACS Style

Aurell, E. On Work and Heat in Time-Dependent Strong Coupling. Entropy 2017, 19, 595.

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