The semiclassical approximation to quantum gravity and its observational consequences

Abstract

We study possible observational effects from the Wheeler-DeWitt equation of quantum geometrodynamics. For this purpose, we perform a semiclassical expansion and derive quantum-gravitational correction terms that are inversely proportional to the Planck mass squared. We apply these results to cosmology and calculate the resulting modification of the CMB power spectrum. Although the correction terms are too small to be currently observable, they could provide the key for future tests of quantum gravity.