Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Practical solutions for perturbed f(R) gravity   We examine the accuracy of the quasi-static approximation and a parametric
form commonly employed for evolving linear perturbations in f(R) gravity
theories and placing cosmological constraints. In particular, we analyze the
nature and the importance of the near horizon effects that are often neglected.
We find that for viable models, with a small present value of the scalaron
field, such corrections are entirely negligible with no impact on observables.
We also find that the one-parameter form, commonly used to represent the
modified equations for linear perturbations in f(R), leads to theoretical
systematic errors that are relatively small and, therefore, is adequate for
placing constraint on f(R) models.

12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol