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Durham University

Department of Mathematical Sciences


Publication details for Kasper Peeters

Nicolai, H., Peeters, K. & Zamaklar, M. (2005). Loop quantum gravity: An Outside view. Classical and Quantum Gravity 22(19): 193-247.

Author(s) from Durham


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 emphasize that the off-shell ('strong') closure of the constraint algebra is a crucial test of quantum spacetime 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.