Speaker
Description
In this talk, I will discuss how the Schwinger–Keldysh formalism can be used to describe out-of-equilibrium effects in false vacuum decay during cosmological phase transitions. By integrating out a thermal UV sector in a scalar $\lambda \phi^4$ toy model, we derive a coarse-grained effective action for the IR modes, whose dynamics is both dissipative and stochastic. Formulating the evolution in phase space leads to a Fokker–Planck-like equation, enabling the evaluation of metastable decay rates using methods pioneered by Kramers and Langer. I will discuss the challenges of this approach, compare this microphysical framework with standard treatments of bubble nucleation, and comment on possible implications for the stochastic gravitational-wave background generated during the phase transition.