Viable Inflationary Evolution from Loop Quantum Cosmology Scalar-Tensor Theory

TL;DR

This paper develops a reconstruction method for Loop Quantum Cosmology scalar-tensor theories based on observational indices, demonstrating viable inflationary models compatible with current data and exploring their classical and quantum limits.

Contribution

It introduces a bottom-up reconstruction technique for LQC scalar-tensor theories using the scalar-to-tensor ratio and analyzes their viability and classical limit.

Findings

The inflationary models are compatible with Planck and BICEP2/Keck-Array data.

The classical limit of the quantum-corrected theory matches the classical theory at leading order.

Various inflationary potentials can be realized within the quantum framework.

Abstract

In this work we construct a bottom-up reconstruction technique for Loop Quantum Cosmology scalar-tensor theories, from the observational indices. Particularly, the reconstruction technique is based on fixing the functional form of the scalar-to-tensor ratio as a function of the $e$-foldings number. The aim of the technique is to realize viable inflationary scenarios, and the only assumption that must hold true in order for the reconstruction technique to work is that the dynamical evolution of the scalar field obeys the slow-roll conditions. We shall use two functional forms for the scalar-to-tensor ratio, one of which corresponds to a popular inflationary class of models, the $\alpha$-attractors. For the latter, we shall calculate the leading order behavior of the spectral index and we shall demonstrate that the resulting inflationary theory is viable and compatible with the latest Planck and BICEP2/Keck-Array data. In addition, we shall find the classical limit of the theory, and as we demonstrate, the Loop Quantum Cosmology corrected theory and the classical theory are identical at leading order in the perturbative expansion quantified by the parameter $\rho_c$, which is the critical density of the quantum theory. Finally, by using the formalism of slow-roll scalar-tensor Loop Quantum Cosmology, we shall investigate how several inflationary potentials can be realized by the quantum theory, and we shall calculate directly the slow-roll indices and the corresponding observational indices. In addition, the $f(R)$ gravity frame picture is presented.