文档介绍：arXiv:hep-th/0601129v2 16 Feb 2006
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1. Quantum Einstein gravity ics approach [7], addresses several aspects of the
problem that are currently outside the main focus
The assumption that Einstein’s classical theory of of string theory, in particular the question of back-
gravity can be quantised non-perturbatively is at the ground independence and the quantisation of geom-
root of a wide variety of approaches to quantum etry. Whereas there is a rather direct link between
gravity. The assumption constitutes the basis of sev- (perturbative) string theory and classical space-time
eral discrete methods [1], such as dynamical tri- concepts, and string theory can therefore rely on fa-
angulations and Regge calculus, but it also implic- miliar notions and concepts, such as the notion of a
itly underlies the older Euclidean path integral ap- particle and the S-matrix, the task is harder for LQG,
proach [2, 3] and the somewhat more indirect ar- as it must face up right away to the question of what
guments which suggest that there may exist a non- an observable quantity is in the absence of a proper
trivial fixed point of the renormalisation group [4–6]. semi-classical space-time with fixed asymptotics.
Finally, it is the key assumption which underlies loop The present text,