Going beyond the Standard paradigm of Cosmology: Torsion, gravitational anomalies and inflation without inflaton fields

TL;DR

This paper presents a string-inspired cosmological model with torsion and gravitational anomalies that naturally induces inflation without inflaton fields, explains matter-antimatter asymmetry, and predicts observable deviations from standard cosmology.

Contribution

It introduces a novel inflationary scenario driven by gravitational anomalies and torsion, eliminating the need for inflaton fields and providing explanations for matter asymmetry.

Findings

Inflation occurs via gravitational wave condensates without inflaton fields.

The model predicts deviations from ΛCDM that could resolve cosmological tensions.

Matter-antimatter asymmetry is generated during the post-inflation era due to Lorentz-violating axion backgrounds.

Abstract

I review a string-inspired cosmological model, with gravitational anomalies present at very early epochs, which includes a totally antisymmetric torsion, that in (3+1)-dimensions is equivalent to a pseudoscalar (Kalb-Ramond, string-model independent) axion field. Upon condensation of primordial gravitational waves (GW), that are created at a pre-inflationary era, the model leads to inflation of the so-called running-vacuum-model (RVM) type, which is realised without the need for external inflaton fields, being due to the non-linearities that characterise the gravitational theory. The model provides an alternative to the $\Lambda$CDM paradigm, and is also capable of inducing matter-antimatter asymmetry in the Universe, during the post-inflationary radiation era, in models with right-handed neutrinos in their matter spectra. The so-induced asymmetry is triggered by a Lorentz-symmetry-violating KR axion background that is generated during the RVM-inflationary period, as a consequence of the GW condensate. The modern era of this cosmology is argued to be characterised by observable (RVM-type) deviations from $\Lambda$CDM, with the potential of alleviating the observed tensions in the cosmological data.