Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Classical Universe Arising from Quantum Cosmology   In this paper, we study the classical limit and unitary evolution of quantum
cosmology by applying the Weyl--Wigner--Groenewold--Moyal formalism of
deformation quantization to quantum cosmology of a homogeneous and isotropic
universe with positive spatial curvature and conformally coupled scalar field.
The corresponding quantum cosmology (similar to the Schr\"{o}dinger
interpretation in canonical quantization scheme of quantum cosmology) is
described by the Moyal--Wheeler--DeWitt equation which has an exact solution in
Moyal phase space, resulting in Wigner quasiprobability distribution function,
peaking over the classical solutions. We show that for a large value of the
quantum number $n$, the emerged classical universe is filled with radiation
with quantum mechanical origin. Also, we introduce a canonical transformation
on the scalar field sector of the model such that the conjugate momenta of the
new canonical variable appear linearly in the transformed total Hamiltonian.
Using this canonical transformation, we show that, it may lead to disentangle
the time from the true dynamical variables. We obtain the time-dependent Wigner
function for a coherent as well as for squeezed states. We show that the peak
of these Wigner functions follows the classical trajectory in the phase space.

9
The categories of this paper are: nlin
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat