language: en

[IOP PUBLISHING]

[CLASSICAL AND QUANTUM GRAVITY]

[Class. Quantum Grav. 25 (2008) 114006 (17pp)]

doi:10.1088/0264-9381/25/11/114006

The emergence of spacetime or quantum gravity on your desktop

R Loll
Institute for Theoretical Physics, Utrecht University,
Leuvenlaan 4, NL-3584 CE Utrecht, The Netherlands
E-mail: r.loll@phys.uu.nl Received 2 November 2007, in final form 18 March 2008 Published 15 May 2008

[Online at stacks.iop.org/CQG/25/114006]

Abstract Is there an approach to quantum gravity which is conceptually simple, relies on very few fundamental physical principles and ingredients, emphasizes geometric (as opposed to algebraic) properties, comes with a definite numerical approximation scheme, and produces robust results, which go beyond showing mere internal consistency of the formalism? The answer is a resounding yes: it is the attempt to construct a nonperturbative theory of quantum gravity, valid on all scales, with the technique of so-called causal dynamical triangulations. Despite its conceptual simplicity, the results obtained up to now are far from trivial. Most remarkable at this stage is perhaps the fully dynamical emergence of a classical background (and solution to the Einstein equations) from a nonperturbative sum over geometries, without putting in any preferred geometric background at the outset. In addition, there is concrete evidence for the presence of a fractal spacetime foam on Planckian distance scales. The availability of a computational framework provides built-in reality checks of the approach, whose importance can hardly be overestimated.

PACS numbers: 04.60.Gw, 04.60.Nc

(Some figures in this article are in colour only in the electronic version)

1. Quantum gravity: aims and ambitions