algebraic quantum field theory (perturbative, on curved spacetimes, homotopical)
quantum mechanical system, quantum probability
interacting field quantization
A vacuum state for an interacting field theory is sometimes called, for emphasis, an interacting vacuum.
In perturbative quantum field theory one starts with a free field theory and a vacuum state (or Hadamard vacuum state) on that, the “free vacuum”; and then finds, perturbatively, the interacting field algebra of observables. The free vacuum is typically still a state on the interacting field algebra of observables, but it is in general no longer a vacuum state with respect to the interacting field algebra. To highlight the difference to an actual vacuum state for the interacting field algebra, one speaks of the interacting vacuum (e.g. Rafelski 90).
Issues related to the adiabatic limit and infrared divergences in perturbative QFT are argued to be related to the need to pass to the correct interacting vacuum (Duch 17, p. 113-114).
This is understood to some extent in quantum electrodynamics but remains a major open problem in quantum chromodynamics (below).
There are arguments that the phenomenon of confinement in QCD will be explained by finding the properly interacting vacuum of the perturbative theory (Rafelski 90, around pages 12-16). Possibly this is a “theta-vacuum” reflecting QCD instanton contributions (Schäfer-Shuryak 98, section III D).
Johann Rafelski, Vacuum structure – An Essay, in pages 1-29 of H. Fried, Berndt Müller (eds.) Vacuum Structure in Intense Fields, Plenum Press 1990 (GBooks)
Thomas Schaefer, Edward Shuryak, Instantons in QCD, Rev. Mod. Phys.70:323-426,1998 (arXiv:hep-ph/9610451)
Paweł Duch, Massless fields and adiabatic limit in quantum field theory (arXiv:1709.09907)
Last revised on May 17, 2019 at 16:05:04. See the history of this page for a list of all contributions to it.