Abstract
The aim of this paper is to provide a general introduction to the problem of time in quantum gravity. This problem originates in the fundamental conflict between the way the concept of ‘time’ is used in quantum theory, and the role it plays in a diffeomorphism-invariant theory like general relativity. Schemes for resolving this problem can be sub-divided into three main categories: (I) approaches in which time is identified before quantising; (II) approaches in which time is identified after quantising; and (III) approaches in which time plays no fundamental role at all. Ten different specific schemes are discussed in this paper which also contain an introduction to the relevant parts of the canonical decomposition of general relativity.
Lectures presented at the NATO Advanced Study Institute “Recent Problems in Mathematical Physics”, Salamanca, June 15–27, 1992.
Research supported in part by SERC grant GR/G60918.
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Isham, C.J. (1993). Canonical Quantum Gravity and the Problem of Time. In: Ibort, L.A., Rodríguez, M.A. (eds) Integrable Systems, Quantum Groups, and Quantum Field Theories. NATO ASI Series, vol 409. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-1980-1_6
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