Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constraints on modified gravity from the observed X-ray luminosity
  function of galaxy clusters   We use measurements of the growth of cosmic structure, as inferred from the
observed evolution of the X-ray luminosity function (XLF) of galaxy clusters,
to constrain departures from General Relativity (GR) on cosmological scales. We
employ the popular growth rate parameterization, Omega_m(z)^gamma, for which GR
predicts a growth index gamma~0.55. We use observations of the cosmic microwave
background (CMB), type Ia supernovae (SNIa), and X-ray cluster gas-mass
fractions (fgas), to simultaneously constrain the expansion history and energy
content of the Universe, as described by the background model parameters:
Omega_m, w, and Omega_k, i.e., the mean matter density, the dark energy
equation of state parameter, and the mean curvature, respectively. Using
conservative allowances for systematic uncertainties, in particular for the
evolution of the mass-luminosity scaling relation in the XLF analysis, we find
gamma=0.51+0.16-0.15 and Omega_m=0.27+-0.02 (68.3 per cent confidence limits),
for a flat cosmological constant (LCDM) background model. Allowing w to be a
free parameter, we find gamma=0.44+0.17-0.15. Relaxing the flatness prior in
the LCDM model, we obtain gamma=0.51+0.19-0.16. When in addition to the XLF
data we use the CMB data to constrain gamma through the ISW effect, we obtain a
combined constraint of gamma=0.45+0.14-0.12 for the flat LCDM model. Our
analysis provides the tightest constraints to date on the growth index. We find
no evidence for departures from General Relativity on cosmological scales.

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The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
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The categories of this paper are: hep-ex
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The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
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The categories of this paper are: stat