Superadiabatic basis in cosmological particle production: application to preheating

TL;DR

This paper investigates how the choice of adiabatic basis affects particle number calculations during cosmological preheating, providing a unified simple connection formula that captures different resonance regimes.

Contribution

It introduces an optimal adiabatic basis and derives a simple connection formula to accurately describe particle production across various parameter regimes.

Findings

The simple connection formula effectively models particle production in both narrow and broad resonance regimes.

The adiabatic basis choice significantly influences the particle number evolution during preheating.

The analysis employs Stokes phenomenon to derive the connection formula, unifying different resonance behaviors.

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.