Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Time in quantum cosmology   A cosmological model with two global internal times shows that time
reparameterization invariance, and therefore covariance, is not guaranteed by
deparameterization. In particular, it is impossible to derive proper-time
effective equations from a single deparameterized model if quantum corrections
from fluctuations and higher moments are included. The framework of effective
constraints shows how proper-time evolution can consistently be defined in
quantum cosmological systems, such that it is time reparameterization invariant
when compared with other choices of coordinate time. At the same time, it
allows transformations of moment corrections in different deparameterizations
of the same model, indicating partial time reparameterization of internal-time
evolution. However, in addition to corrections from moments such as quantum
fluctuations, also factor ordering corrections may appear. The latter
generically break covariance in internal-time formulations. Fluctuation effects
in quantum cosmology are therefore problematic, in particular if derivations
are made with a single choice of internal time or a fixed physical Hilbert
space.

4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
19
The categories of this paper are: eess
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex