Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Wave Packet in Quantum Cosmology and Definition of Semiclassical Time   We consider a quantum cosmology with a massless background scalar field $\pb$
and adopt a wave packet as the wave function. This wave packet is a
superposition of the WKB form wave functions, each of which has a definite
momentum of the scalar field $\pb$. In this model it is shown that to trace the
formalism of the WKB time is seriously difficult without introducing a complex
value for a time. We define a semiclassical real time variable $\tp$ from the
phase of the wave packet and calculate it explicitly. We find that, when a
quantum matter field $\pq$ is coupled to the system, an approximate
Schr\"odinger equation for $\pq$ holds with respect to $\tp$ in a region where
the size $a$ of the universe is large and $|\pb|$ is small.

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The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th