Superadiabatic basis in cosmological particle production: application to preheating

Abstract

We discuss the adiabatic basis dependence of particle number in time-dependent backgrounds. In particular, we focus on preheating after inflation, and show that, for the optimal basis, the time dependence of the produced particle number can be well approximated by a simple connection formula, which can be obtained by analysing Stokes phenomenon in given backgrounds. As we show explicitly, the simple connection formula can describe various parameter regions such as narrow and broad resonance regime in a unified manner.

QFT approach to dressed particle processes in preheating and non-perturbative mechanism in kinematically-forbidden regime

“…2, the compact formula (2.31) may be a bit unsatisfactory as the background fields are Taylor expanded up to only the lowest order ∼ t and hence non-linear effects beyond the linear approximation, which can be important for non-adiabatic fields, cannot be described. For instance, our treatment cannot be applied when multiple particle production events equally contribute to particle production, for which, e.g., quantum interference between different production events occur and the production number is significantly modified [25,[40][41][42][43][44][45][46][47][48][49][50][51]. Such a multiple particle production would be relevant in the preheating, e.g., if the parent particle is light so that the exponential suppression in the parent particle-number density is not small enough.…”

“…A possible avenue to deal with more general background fields is semi-classical methods. Indeed, recent developments in understanding of the WKB method [25,42,[46][47][48][51][52][53][54][55][56] would enable us to address the non-perturbative dressed mode function in more general backgrounds. The semi-classical approach would also help us to develop more physical understandings of the kinematically-forbidden process (e.g., the production time).…”