Since the standard inflationary paradigm is based on quantum field theory on classical space-times, it excludes the Planck era. Using techniques from loop quantum gravity, the theory is extended to overcome this limitations. The new framework sharpens conceptual issues by distinguishing between the true and apparent trans-Planckian difficulties and provides sufficient conditions under which the true difficulties can be overcome within a quantum gravity theory, with interesting lessons for both theory and observations.
Laboratoire de Physique Subatomique et de Cosmologie de Grenoble
In this talk, I'll briefly review some possible observational consequences of loop quantum gravity. I will first address the issue of the closure of the algebra of constraints in holonomy-corrected effective loop quantum cosmology for tensor, vector, and scalar modes. I will underline some unexpected features like a possible change of signature. The associated primordial power spectrum and the basics of the related CMB analysis will be presented. The "asymptotic silence" hypothesis will be mentioned as a promising alternative. Then, I'll address the issue of the probability for inflation and the prediction of its duration from a new perspective. Finally, I'll present some prospect about the evaporation of black holes in LQG.
I review the main properties of the Gamma Ray Bursts (GRBs) as possible sources of high energy (E>TeV) neutrinos and confirmed sources of high energy (E>GeV) photons. I discuss the possibility to use the data of neutrino telescopes, such as IceCube and the GeV-photon telescopes, such as Fermi’s LAT, for precision tests of Einstein's Special Relativity as applied to neutrinos and photons. My focus is on possible departures from Special Relativity that can be motivated by models of quantum space-time. I observe that neutrinos which one would not associate to a GRB, when assuming a classical spacetime picture, may well be GRB neutrinos if the possibility that Lorentz invariance is broken at very high energies is taken into account. I outline how future analyses of neutrino data should be done in order to systematically test the Lorentz Invariance Violation possibility. In addition I consider the possibility that Lorentz Invariance Violation might be responsible for the spectral lags that characterize the GeV signal observed for the remarkable GRB130427A. A comparison of these features for GRBs at different redshifts provides some encouragement for a redshift dependence of the effects of the type expected for a quantum-spacetime interpretation, but other aspects of the analysis appear to invite the interpretation as intrinsic properties of GRBs.