Analytical investigation of pre-inflationary effects in the primordial power spectrum: From General Relativity to hybrid Loop Quantum Cosmology

Abstract

This work is an analytical study of the main differences between classical inflationary effects of a fast-roll regime and imprints of hybrid Loop Quantum Cosmology (LQC) on the primordial power spectrum. Effective LQC solutions of phenomenological interest typically contain a classical period of kinetic dominance prior to slow-roll inflation, with consequences on the power spectrum that here we try and tell apart from those of phenomena occuring in the vicinity of a bounce in hybrid LQC. For this comparison, we use the same criterion for the choice of a vacuum state of the primordial perturbations, both in the context of relativistic cosmology and on the LQC cosmological background. As a first approximation to the problem, our study ignores the influence of a quasi-de Sitter evolution (rather than de Sitter) in the slow-roll inflationary regime, and of a typically short transition between the kinetically dominated era and the slow-roll period. Our results show that, while the two studied types of effects can lead to a drastic power suppression in the infrared sector of the spectrum, the mode scale at which this happens is much larger for LQC than for classical relativistic cosmology, the corresponding scales being related to the spacetime curvature at the bounce and at the onset of inflation, respectively.

This is the Accepted Manuscript version of an article accepted for publication in Journal of Cosmology and Astroparticle Physics. Neither SISSA Medialab Srl nor IOP Publishing Ltd is responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.1088/1475-7516/2021/09/030

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• Choice of vacuum state and the relation between inflationary and Planck scales
• Polar perturbations in Kantowski-Sachs spacetimes and hybrid quantum cosmology
• Effects of the inflaton potential on the primordial power spectrum in Loop Quantum Cosmology scenarios
• Covariant Predictions for Planck-Scale Features in Primordial Power Spectra
• Primordial perturbations in kinetically dominated regimes of general relativity and hybrid quantum cosmology
• On the evolution of the volume in Loop Quantum Cosmology