A well-studied model in open quantum system theory is a system interacting with a thermal bath of harmonic oscillators at finite temperature. This provides a quantum mechanical model of a classical resistive element in a circuit, and includes as a famous example the "spin-boson model". Such environments however also include baths of thermal photons and phonons. As long as the environment consists of harmonic oscillators interacting linearly with the system, and starting in a thermal state, the environmental degrees of freedom can be integrated out using the Feynman-Vernon method.
I will present the open system dynamics of a test particle interacting linearly with a thermal bath of photons, following [1] and [2]. I will then discuss the energy change of the bath (quantum heat) using an approach now standard in quantum thermodynamics. I will further discuss what one can say if the bath temperature is very low or zero, i.e. if the test particle interacts with the vacuum. I will end by discussing what this says or does not say about the entropy production in the electro-magnetic vacuum.
The seminar will be given in hybrid format, on-line at
https://kth-se.zoom.us/j/68888238166
[1] Heinz-Peter Breuer and Francesco Petruccione, "Destruction of quantum coherence through emission of bremsstrahlung", Phys. Rev. A 63, 032102 (2001)
[2] Heinz-Peter Breuer and Francesco Petruccione, Theory of Open Quantum Systems (2002), Chapter 12