Oscillating scalar dissipating in a medium

A bstract We study how oscillations of a scalar field condensate are damped due to dissipative effects in thermal medium. Our starting point is non-linear and non-local equation motion descending from 2PI-resummed effective action derived the Schwinger-Keldysh formalism appropriate for non-equilibrium quantum theory. solve this by means multiple-scale perturbation theory time-dependent systems, obtaining approximate analytic solutions valid very long times. The lead power-law damping oscillations, that at late times transition exponentially ones characteristic linear systems. These describe evolution well, as we demonstrate numerically number examples. then Markovianised one, resolving ambiguities appearing process, it utilizing same methods find leading solution. This comparison justifies use Markovian equations order. standard not capable describing beyond early time regime negligible damping. macroscopic interpreted terms microphysical particle processes. results have implications quantitative description decay cosmological fields Universe, may also be applied other physical