Observational imprints from Loop Quantum Cosmology

TL;DR

This paper explores how Loop Quantum Cosmology's quantum bounce could leave observable imprints on the Cosmic Microwave Background, providing insights into pre-inflationary physics beyond standard cosmology.

Contribution

It investigates potential observational signatures of LQC's pre-inflationary dynamics in the CMB using the hybrid approach to cosmological perturbations.

Findings

Possible excited states of modes at inflation onset due to LQC effects

Imprints in the power spectra of CMB anisotropies

Constraints on quantum bounce models from observational data

Abstract

The standard model of cosmology assumes a homogeneous and isotropic universe that undergoes a period of exponential expansion very early on, named inflation. This stretches quantum fluctuations from the onset of inflation to cosmological scales, which seed the temperature, polarization and matter anisotropies that we observe. However, this paradigm ignores pre-inflationary physics, as shortly before inflation there is the initial big-bang singularity. Loop Quantum Cosmology (LQC) is a promising approach to quantum cosmology. Its most outstanding result is that of the resolution of the classical initial singularity in terms of a quantum bounce that connects a contracting branch of the Universe with an expanding one. Consequently, it provides singularity-free pre-inflationary dynamics. Within this context, it is no longer justified to consider that every mode of the cosmological perturbations reaches the onset of inflation in the natural vacuum state of standard cosmology. In fact, some modes might reach it in an excited state, which may leave imprints in their power spectra at the end of inflation and therefore in observations of the Cosmic Microwave Background (CMB). The goal of this thesis is to search for such imprints from LQC in the CMB. We work in the hybrid approach to cosmological perturbations in LQC.