Quantum corrections to the primordial tensor spectrum: Open EFTs & Markovian decoupling of UV modes

Abstract: Perturbative quantum corrections to primordial power spectra are important for testing the robustness and the regime of validity of inflation as an effective field theory. Although this has been done extensively for the density power spectrum (and, to some extent, for the tensor spectrum) using loop corrections, we do so in an open quantum system approach to the problem. Specifically, we calculate the first order corrections to the primordial gravitational wave spectrum due to (cubic) tensor interactions alone. We show that our results match expectations from standard loop corrections only in the strict Markovian limit, and therefore, establish a systematic way to relax this approximation in the future, as is generally necessary for gravitational systems.