Nearly universal CMB TT spectrum from pre-inflationary dynamics in a closed universe: KICI scenario, bouncing universe, and emergent universe

TL;DR

This paper analyzes the early universe's dynamics in a closed universe model, showing that different pre-inflationary scenarios produce nearly identical CMB TT spectra with large-scale suppression.

Contribution

It introduces a phase space analysis of closed universe evolution, revealing three distinct paths leading to similar CMB signatures regardless of pre-inflationary details.

Findings

Primordial power spectrum and CMB TT spectrum are suppressed at large scales.

Different pre-inflationary models produce indistinguishable CMB TT spectra.

Suppression and shape of the spectra are independent of specific pre-inflationary dynamics.

Abstract

We utilize the phase space analysis method to study the early evolution of the spatially closed universe and find that there exists an attractor denoting the de Sitter expansion phase, and that the universe has three distinct evolutionary paths, which correspond to the kinetic initial conditions for inflation (KICI) scenario, bouncing universe, and emergent universe. Based on the results of the phase space analysis, we calculate the primordial power spectrum and CMB TT spectrum for these models. We find that, for these models, the primordial power spectrum and CMB TT spectrum are suppressed at large scales. Moreover, the CMB TT spectra for these models overlap completely, indicating that these models are indistinguishable via their CMB TT spectra, and that the suppression and the detailed shape of the CMB TT spectrum are independent of the specific pre-inflationary dynamics or the presence of a transition stage.