Curved space equilibration vs. flat space thermalization (a short review)

Abstract

We discuss equilibration process in expanding universes as compared to the thermalization process in Minkowski space--time. The final goal is to answer the following question: Is the equilibrium reached before the rapid expansion stops and quantum effects have a negligible effect on the background geometry or stress--energy fluxes in a highly curved early Universe have strong effects on the expansion rate and the equilibrium is reached only after the drastic decrease of the space--time curvature? We argue that consideration of more generic non--invariant states in theories with invariant actions is a necessary ingredient to understand quantum field dynamics in strongly curved backgrounds. We are talking about such states in which correlation functions are not functions of such isometry invariants as geodesic distances, while having correct UV behaviour. The reason to consider such states is the presence of IR secular memory effects for generic time dependent backgrounds, which are totally absent in equilibrium. These effects strongly affect the destiny of observables in highly curved space--times.

arXiv comment15 pages

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• Enhancement of particle creation in nonlinear resonant cavities
• Loop corrections to a cosmological particle creation
• Is the Euclidean path integral always equal to the thermal partition function?
• Loop corrections to the current of created pairs in the lengthy electric pulse
• On generalization of 2d gravity with the simplest non-invariant states
• De Sitter entropy: on-shell versus off-shell
• The Propagator Matrix Reloaded