Teleparallel Cosmology – From theory to observational constraints

Speaker: Prof. Jackson Levi Said, Department of Physics, University of Malta, Malta

Standard gravity expresses gravitational effects by curving spacetime about matter. It does this through the Levi-Civita connection which is what produces the curvature feature. However, this is not the only choice, there also exists the teleparallel connection through which gravitation exhibits a torsional behaviour. Teleparallel gravity can be constructed to be dynamically equivalent to regular general relativity (GR), known as the teleparallel equivalent to general relativity (TEGR). As in standard GR, one can modify the gravitational theory and consider beyond GR theories. While GR and TEGR are dynamically equivalent, their modifications are not for the most part. In this way, modifications of TEGR are novel and have shown to produce behaviour different to the traditional modifications of gravity. In cosmology, these proposals have shown to produce models beyond GR that can compete with GR in a number of important ways that range from their gravitational wave polarization signatures to their ability to produce the correct expansion dynamics across the cosmological history of the Universe, among others. In this presentation, we will cover the salient features of teleparallel gravity and its key observational predictions in the cosmological regime. We will discuss the confrontation of teleparallel models with the most recent observational surveys and the corresponding constraints on the corresponding beyond GR models. We will close with a discussion on areas to expect the theory to be further developed in and where it can become even more competitive with GR in the coming years.