Speaker
Description
Equal-time in-in correlation functions are important observables for cosmological models and quantum field theories. In this talk, I will first explore how the Wilsonian renormalization group and effective field theory (EFT) apply to these observables in both flat and de Sitter space. Specifically, matching the UV and IR requires additional terms not captured by conventional EFT. These terms are localized at the time of the measurement, and (semi-)local in space. Explicit examples show how matching is done in flat spacetime, and that in de Sitter spacetime these terms redshift away, with suspected remnant effects on wavefunction coefficients. I will then discuss these terms from a Schwinger-Keldysh path integral point of view, and study their roles in the influence functional, making connections to the evolution of the density matrix. Some future works will be discussed at the end.