Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A complete study of conformally flat pseudo-symmetric spacetimes in the
  theory of F(R)-gravity   We investigate the geometrical and physical structures of a pseudo-symmetric
spacetime $(PS)_4$ with timelike vector under the condition of conformal
flatness. We classify it into two possible types: constant Ricci scalar and
closed velocity vector. We further study this spacetime as a solution of
$F(R)$-gravity theory and show that the pressure and energy density of the
effective cosmological perfect fluid separately possess certain typical
relations with the geometry and the gravity sector of the theory. Based on this
result, some observational and cosmological analyses are done for the
$F(R)$-gravity model and the energy conditions are investigated, supporting the
accelerated expansion of the universe.

8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
22
The categories of this paper are: chao-dyn
28
The categories of this paper are: alg-geom
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol