Quantum Open System Formulation of Stochastic Inflation
This work formulates stochastic inflation using an open quantum system approach. By treating the coarse-grained field and momentum in a patch as a quantum system, the entanglement with external modes induces non-unitary evolution. This leads to GKLS dynamics in de Sitter space, unifying diffusion and Hubble friction within a single quantum channel, and is shown to be equivalent to classical Fokker-Planck equations under specific limits. The framework distinguishes between light and heavy fields, with heavy fields resisting classical stochastic descriptions due to maintained purity.