Quantum Gravity: Has Spacetime Quantum Properties?
Abstract
The incompatibility between GR and QM is generally seen as a sufficient motivation for the development of a theory of Quantum Gravity. If  so a typical argumentation  QM gives a universally valid basis for the description of all natural systems, then the gravitational field should have quantum properties. Together with the arguments against semiclassical theories of gravity, this leads to a strategy which takes a quantization of GR as the natural avenue to Quantum Gravity. And a quantization of the gravitational field would in some sense correspond to a quantization of geometry. Spacetime would have quantum properties. But, this strategy will only be successful, if gravity is a fundamental interaction.  What, if gravity is instead an intrinsically classical phenomenon? Then, if QM is nevertheless fundamentally valid, gravity can not be a fundamental interaction. An intrinsically classical gravity in a quantum world would have to be an emergent, induced or residual, macroscopic effect, caused by other interactions. The gravitational field (as well as spacetime) would not have any quantum properties. A quantization of GR would lead to artifacts without any relation to nature. The serious problems of all approaches to Quantum Gravity that start from a direct quantization of GR or try to capture the quantum properties of gravity in form of a 'graviton' dynamics  together with the, meanwhile, rich spectrum of approaches to an emergent gravity and/or spacetime  make this latter option more and more interesting for the development of a theory of Quantum Gravity. The most advanced emergent gravity (and spacetime) scenarios are of an informationtheoretical, quantumcomputational type.
 Publication:

arXiv eprints
 Pub Date:
 February 2009
 DOI:
 10.48550/arXiv.0902.0190
 arXiv:
 arXiv:0902.0190
 Bibcode:
 2009arXiv0902.0190H
 Keywords:

 General Relativity and Quantum Cosmology
 EPrint:
 31 pages