“Cosmic Acceleration as a Quantum Gravity Effect”

null, Ward Struyve

Abstract: Bohmian quantum gravity is a non-classical geometrodynamics (in the ADM formalism) which describes the time evolution of a 3-geometry and of a matter field (or other matter degrees of freedom). One of the virtues of this theory is that it solves the problem of time of quantum gravity. The Bohmian dynamics also entails novel features compared to classical geometrodynamics (i.e., general relativity), such as singularity avoidance and the possibility of accelerated expansion as a quantum effect. We will consider the latter in a simplified model of quantum gravity using a mini-superspace description of an isotropic and homogeneous universe with dust. We derive the modified Friedmann equations for the scale factor, which now contain a dependence on the wave function. We identify wave functions for which the quantum effects lead to a period of accelerated expansion that is in agreement with the apparent evolution of our universe, without introducing a cosmological constant.