Loop quantum gravity: an outside view
Abstract
We review aspects of loop quantum gravity in a pedagogical manner, with the aim of enabling a precise but critical assessment of its achievements so far. We emphasise that the off-shell (`strong') closure of the constraint algebra is a crucial test of quantum space-time covariance, and thereby of the consistency, of the theory. Special attention is paid to the appearance of a large number of ambiguities, in particular in the formulation of the Hamiltonian constraint. Developing suitable approximation methods to establish a connection with classical gravity on the one hand, and with the physics of elementary particles on the other, remains a major challenge.
Keywords
Cite
@article{arxiv.hep-th/0501114,
title = {Loop quantum gravity: an outside view},
author = {Hermann Nicolai and Kasper Peeters and Marija Zamaklar},
journal= {arXiv preprint arXiv:hep-th/0501114},
year = {2009}
}
Comments
57 pages, 11 figures; v2: substantially revised, references added, resubmitted to Class. Quant. Grav.; v3: further substantial improvements; v4: small changes, final version to appear in Class. Quant. Grav