Time and a physical Hamiltonian for quantum gravity

Phys Rev Lett. 2012 Apr 6;108(14):141301. doi: 10.1103/PhysRevLett.108.141301. Epub 2012 Apr 5.

Abstract

We present a nonperturbative quantization of general relativity coupled to dust and other matter fields. The dust provides a natural time variable, leading to a physical Hamiltonian with spatial diffeomorphism symmetry. The surprising feature is that the Hamiltonian is not a square root. This property, together with the kinematical structure of loop quantum gravity, provides a complete theory of quantum gravity, and puts applications to cosmology, quantum gravitational collapse, and Hawking radiation within technical reach.