Boltzmann or Bogoliubov? Approaches Compared in Gravitational Particle Production

Understand

Gravitational particle production is a minimal contribution to reheating the Universe after the end of inflation.

• To study this production channel, two different approaches have commonly been considered, one of which is based on the Boltzmann equation, and the other is based on the Bogoliubov transformation.
• Each of these has pros and cons in practice.
• The collision term in the Boltzmann equation can be computed based on quantum field theory in the Minkowski spacetime, and thus many techniques have been developed so far.