Comparing Inflationary Models in Extended Metric-Affine Theories of Gravity

TL;DR

This paper compares inflationary models within extended metric-affine theories of gravity, analyzing their predictions against observational data to identify potential signatures that distinguish different geometric frameworks of gravity.

Contribution

It provides a comprehensive comparison of inflationary scenarios across various extended metric-affine gravity models using dual approaches and observational constraints.

Findings

Constraints on model parameters from Planck 2018 and BICEP2/Keck data

Differences in inflationary predictions among extended gravity theories

Qualitative distinctions between the three classes of modified gravity

Abstract

We study slow-roll inflation as a common feature in Metric-affine Theories of Gravity. In particular, we take into account extended metric, teleparallel and symmetric-teleparallel theories of gravity, based on different geometric invariants, discussing analogies and differences. The analysis for each model is performed in two approaches. First, we focus on the {\it potential-slow-roll approach} by studying the reconstructed potentials for different forms of the extended models related to the considered gravitational theory in the Einstein frame. Secondly, we investigate the {\it Hubble-slow-roll approach} for some conventional inflationary potentials related to the specific extended model in the Jordan frame. We compare all results with cosmic microwave background anisotropy observations coming from Planck 2018 and BICEP2/Keck array satellites in order to find the observational constraints on the parameters space of the models as well as their prediction from the spectral parameters. Eventually, we attempt to present a qualitative comparison between three classes of considered modified gravities using the obtained inflationary results. The aim is to select, in principle, cosmological signatures capable of discriminating among concurrent models in view to point out the representation of gravity, according with geometric invariants, which better addresses the early universe dynamics.