Dark energy from the gravity vacuum
Abstract
We propose a new solution to the cosmological constant problem building on a nonperturbative quantum theory of gravity with torsional instantons. These pseudoparticles, which were recently found to exist in a first order formulation of GiddingsStrominger axionic gravity, carry nontrivial NiehYan topological charge. The nonperturbative ground state as generated due to tunneling effects is shown to be stable under quantum fluctuations. Within this framework, the associated vacuum angle, namely the BarberoImmirzi topological parameter, gets fixed to a numerical value determined by the Hubble constant.
 Publication:

Classical and Quantum Gravity
 Pub Date:
 October 2015
 DOI:
 10.1088/02649381/32/19/195005
 arXiv:
 arXiv:1501.00779
 Bibcode:
 2015CQGra..32s5005S
 Keywords:

 cosmological constant;
 nonperturbative quantum gravity;
 torsional instantons;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 Matches the version to be published in Class. Quantum Grav.