Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Back Reaction and Semiclassical Approximation of cosmological models
  coupled to matter   Bianchi -I, -III, and FRW type models minimally coupled to a massive
spatially homogeneous scalar field (i.e. a particle) are studied in the
framework of semiclassical quantum gravity. In a first step we discuss the
solutions of the corresponding equation for a Schr\"odinger particle
propagating on a classical background. The back reaction of the Schr\"odinger
particle on the classical metric is calculated by means of the Wigner function
and by means of the expectation value of the energy-momentum-tensor of the
field as a source. Both methods in general lead to different results.

32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
2
The categories of this paper are: math
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
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
35
The categories of this paper are: mtrl-th