Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quantum cosmology and the emergence of a classical world   This paper gives an elementary introduction to some of the conceptual
problems of quantum cosmology. Contents: 1. Why quantum cosmology? 2. Time in
quantum gravity 3.Decoherence and the recovery of the Schrodinger equation 4.
The direction of time

11
The categories of this paper are: hep-lat
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci