Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Cluster Constraints on f(R) Gravity   Modified gravitational forces in models that seek to explain cosmic
acceleration without dark energy typically predict deviations in the abundance
of massive dark matter halos. We conduct the first, simulation calibrated,
cluster abundance constraints on a modified gravity model, specifically the
modified action f(R) model. The local cluster abundance, when combined with
geometric and high redshift data from the cosmic microwave background,
supernovae, H_0 and baryon acoustic oscillations, improve previous constraints
by nearly 4 orders of magnitude in the field amplitude. These limits correspond
to a 2 order of magnitude improvement in the bounds on the range of the force
modification from the several Gpc scale to the tens of Mpc scale.

16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con