Quantum Gravity and Inflation

Abstract

We review some perturbative results obtained in quantum gravity in an accelerating cosmological background. We then describe a class of non-local, purely gravitational models which have the correct structure to reproduce the leading infrared logarithms of quantum gravitational back-reaction during the inflationary regime. These models end inflation in a distinctive phase of oscillations with slight and short violations of the weak energy condition and should, when coupled to matter, lead to rapid reheating. By elaborating this class of models we exhibit one that has the same behaviour during inflation, goes quiescent until the onset of matter domination, and induces a small, positive cosmological constant of about the right size thereafter. We also briefly comment on the primordial density perturbations that this class of models predict.

28 pages, 6 figures, lectures given at the 6th Aegean Summer School in Naxos, Greece, September 12-17, 2011 Version 2 has some typos corrected

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• Nonlocal Cosmology II --- Cosmic acceleration without fine tuning or dark energy
• Nonlocal Metric Realizations of MOND
• A Caveat on Building Nonlocal Models of Cosmology
• Phase Space description of Nonlocal Teleparallel Gravity
• Quantum Cosmology Near Two Dimensions
• Precision Predictions for the Primordial Power Spectra of Scalar Potential Models of Inflation
• Quantum Weyl Invariance and Cosmology
• Strong restriction on inflationary vacua from the local gauge invariance III: Infrared regularity of graviton loops
• From Non-trivial Geometries to Power Spectra and Vice Versa
• An Improved Cosmological Model
• Does nonlocal gravity yield divergent gravitational energy-momentum fluxes?
• Quantum Cosmology in Four Dimensions
• Spherically symmetric static solutions, newtonian potential and degrees of freedom of a Nonlocal action
• The Case for Nonlocal Modifications of Gravity