Unexciting classical backgrounds
Abstract
Quantum fields in timedependent backgrounds generally lead to particle production. Here we consider "unexciting" backgrounds for which the net particle production vanishes. We start by considering the simple harmonic oscillator and explicitly construct all unexciting timedependent frequencies. This allows us to construct homogeneous backgrounds in field theory for which there is no particle production in any given mode, though we are able to show that there are no homogeneous backgrounds for which the particle production vanishes in every mode. We then construct general inhomogeneous unexciting field theory backgrounds. The set of all unexciting field theory backgrounds will be further restricted by the choice of physical interactions and this leads to an interesting open problem.
 Publication:

Physical Review D
 Pub Date:
 March 2022
 DOI:
 10.1103/PhysRevD.105.056008
 arXiv:
 arXiv:2201.02196
 Bibcode:
 2022PhRvD.105e6008V
 Keywords:

 High Energy Physics  Theory;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology
 EPrint:
 7 pages, 4 figures. v2: included further comments and updated references