Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: What is Dynamics in Quantum Gravity?   The appearance of Hamiltonian constraint in the canonical formalism for
general relativity reflects the lack of a fixed external time. The dynamics of
general relativistic systems can be expressed with respect to an arbitrarily
chosen internal degree of freedom, the so called internal clock. We investigate
the way in which the choice of internal clock determines the quantum dynamics
and how much different quantum dynamics induced by different clocks are. We
develop our method of comparison by extending the Hamilton-Jacobi theory of
contact transformations to include a new type of transformations which
transform both the canonical variables and the internal clock. We employ our
method to study the quantum dynamics of the Friedmann-Lemaitre model and obtain
semiclassical corrections to the classical dynamics, which depend on the choice
of internal clock. For a unique quantisation map we find the abundance of
inequivalent semiclassical corrections induced by quantum dynamics taking place
in different internal clocks. It follows that the concepts like minimal volume,
maximal curvature and the number of quantum bounces, often used to describe
quantum effects in cosmological models, depend on the choice of internal clock.

21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
2
The categories of this paper are: math
19
The categories of this paper are: eess