General Markovian equation for scalar fields in a slowly evolving background. Issue 5 (1st May 2022)

• Record Type: Journal Article
• Authors: Buldgen, Gilles; Drewes, Marco; Kang, Jin U; Ri Mun, Ui
• Is Part Of: Journal of cosmology and astroparticle physics. Volume 2022:Issue 5(2022)
• Publication Date: 2022-05-01
• Subjects: particle physics - cosmology connection -- physics of the early universe -- alternatives to inflation -- inflation; Cosmology -- Periodicals; Astrophysics -- Periodicals; 523.0105
• DOI: 10.1088/1475-7516/2022/05/039
• Languages: English
• ISSNs: 1475-7516

Abstract

Abstract: We present a general and model-independent method to obtain an effective Markovian quantum kinetic equation for the expectation value of a slowly evolving scalar field in an adiabatically evolving background from first principles of nonequilibrium quantum field theory. The method requires almost no assumptions about the field's interactions and the composition of the background, except that 1) the coupling constants shall be small enough for perturbation theory to be applicable, 2) there is a clear separation between microphysical time scales and the rate at which bulk properties change, and 3) higher time derivatives of the field remain small. The resulting Markovian equation of motion is expressed in terms of an effective potential and friction coefficients. Motivated by cosmological applications we focus on spatially homogeneous and isotropic systems, but the approach could also be applied to spatial gradients.