Non-relativistic QED at positive temperature

Oliver Siebert 

In the context of non-relativistic Quantum Electrodynamics (QED), one explores the behavior of one or a few quantum mechanical particles, such as atoms and electrons, interacting with a quantized radiation field. Two important phenomena in such systems at positive temperature are 'return to equilibrium,' wherein the entire system approaches thermal equilibrium as time tends towards infinity, and 'thermal ionization,' the eventual ionization of an atom due to high-energy photons in an electromagnetic field. The mathematical treatment of these phenomena involves the spectral theory of Liouvillians, whose spectrum spans the entire real line, and operator algebras arising from infinitely extended equilibrium states."