Astrophysical and cosmological signatures of Loop Quantum Gravity

Abstract

The loop quantum gravity theory is a background-independent and non-perturbative quantization of general relativity. It has been developed both in the canonical and covariant formalisms. As for all tentative theories of quantum gravity, one of the key question is to produce clear experimental or observational predictions. As the discrete nature of spacetime at the Planck scale is extremely difficult to probe directly, phenomenological attempts do focus mostly on the cosmological sector, on black holes and on possible high energy astrophysics effects. The main prediction of loop quantum gravity in the cosmological sector is that the Big Bang is replaced by a Big Bounce: a contracting phase should have taken place before the expanding phase we are now living in. In the black hole sector, the Hawking evaporation spectrum should receive substantial corrections and the very existence of an event horizon can be questioned, potentially leading to black holes bouncing into white holes. Finally, on the astroparticle physics side, the quantum discreteness of spacetime could lead to interesting effects for high energy cosmic rays.