Palatini approach to bouncing cosmologies and DSR-like effects

TL;DR

This paper demonstrates that a quadratic Palatini gravity model can mimic quantum gravity effects like DSR and Rainbow Gravity, avoid big bang singularities, and is free from common issues like the soccer ball problem.

Contribution

It introduces a quadratic Palatini gravity framework that captures quantum gravity phenomenology, including energy-dependent metrics and singularity avoidance, without the soccer ball problem.

Findings

Different energy densities perceive different metrics.

The theory avoids the big bang singularity.

It shares features with loop quantum cosmology.

Abstract

It is shown that a quadratic gravitational Lagrangian in the Palatini formulation is able to capture different aspects of quantum gravity phenomenology in a single framework. In particular, in this theory field excitations propagating with different energy-densities perceive different background metrics, a fundamental characteristic of the DSR and Rainbow Gravity approaches. This theory, however, avoids the so-called soccer ball problem. Also, the resulting isotropic and anisotropic cosmologies are free from the big bang singularity. This singularity avoidance occurs non-perturbatively and shares some similitudes with the effective dynamics of loop quantum cosmology.