Markovian dynamics in de Sitter

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