Quantum field theory in a de Sitter universe transiting to the radiation stage

TL;DR

This paper investigates the evolution of quantum vacuum states and the power spectrum during the universe's transition from an inflationary de Sitter phase to a radiation-dominated stage, providing insights into particle creation and cosmological perturbations.

Contribution

It introduces a methodology to analyze the evolution of vacuum states and power spectra across the de Sitter to radiation transition, linking static de Sitter particle creation to cosmological dynamics.

Findings

Power spectrum changes during the transition for comoving observers

Methodology to transfer particle creation results from static de Sitter to radiation stage

Insights into the evolution of primordial vacuum states

Abstract

We study some physical aspects of quantum field theory in a two stage universe starting from the inflationary de Sitter and transiting into the radiation dominated stage. We look into the time evolution of the primordial vacuum states, associated with the (i) comoving and (ii) Bunch-Davies modes. We show how the power spectrum for a comoving observer, obtained from the excitation of the aforementioned states defined in the de Sitter stage, changes as the universe transits into the radiation stage. In addition, we also develop a methodology to transfer the well known result of particle creation in the static de Sitter frame, originating from the aforementioned vacuum states, while the universe makes a transition to the next (radiation dominated) stage.