Markovian dynamics in de Sitter

The equilibrium state of fields in the causal wedge of a dS observer is thermal, though realistic observers have only partial access to the state. To them, out-of-equilibrium states of a light scalar field appear to thermalize in a Markovian fashion. We show this by formulating a systematic expansion for tracing out the environment. As an example, we calculate the O(lambda) correction to the result of Starobinsky and Yokoyama for the relaxation exponents of lambda phi(4) theory.

Automated summary

By tracing out the environment systematically, we demonstrated the thermalization of out-of-equilibrium states of a light scalar field in a Markovian fashion as perceived by realistic observers. Using the results of Starobinsky and Yokoyama as a case study, we calculated the O(lambda) correction to the relaxation exponents of the lambda phi(4) theory.