Palatini Actions and Quantum Gravity Phenomenology

TL;DR

This paper introduces a covariant gravitational theory using the Palatini approach that incorporates a universal length scale, capturing quantum gravity phenomenology and avoiding singularities like the big bang bounce.

Contribution

It presents a novel covariant framework with an invariant length scale that models quantum gravity effects and resolves the soccer ball problem.

Findings

Different energy-density excitations perceive different metrics.

The theory avoids the soccer ball problem.

Cosmological models exhibit a big bounce instead of a singularity.

Abstract

We show that an invariant an universal length scale can be consistently introduced in a generally covariant theory through the gravitational sector using the Palatini approach. The resulting theory is able to capture different aspects of quantum gravity phenomenology in a single framework. In particular, it is found that in this theory field excitations propagating with different energy-densities perceive different background metrics, which is a fundamental characteristic of the DSR and Rainbow Gravity approaches. We illustrate these properties with a particular gravitational model and explicitly show how the {\it soccer ball problem} is avoided in this framework. The isotropic and anisotropic cosmologies of this model also avoid the big bang singularity by means of a big bounce.