1,572 research outputs found
Particle creation in a f(R) theory with cosmological constraints
In this paper we study the creation of super-massive real scalar particles in
the framework of a modified gravity theory, with parameters
constrained by observational data. The analysis is restrict to a homogeneous
and isotropic flat and radiation dominated universe. We compare the results to
the standard Einstein gravity with cosmological constant ( model),
and we show that the total number density of created particles in the
model is very close to the standard case. Another interesting result is that
the spectrum of created particles is independent at early times.Comment: To appear in the General Relativity and Gravitation. arXiv admin
note: text overlap with arXiv:1108.334
Constraints on the duality relation from ACT cluster data
The cosmic distance-duality relation (CDDR), , where and and are, respectively, the
luminosity and the angular diameter distances, holds as long as the number of
photons is conserved and gravity is described by a metric theory. Testing such
hypotheses is, therefore, an important task for both cosmology and fundamental
physics. In this paper we use 91 measurements of the gas mass fraction of
galaxy clusters recently reported by the Atacama Cosmology Telescope (ACT)
survey along with type Ia supernovae observations of the Union2.1 compilation
to probe a possible deviation from the value . Although in agreement
with the standard hyphothesis, we find that this combination of data tends to
favor negative values of which might be associated with some physical
processes increasing the number of photons and modifying the above relation to
.Comment: 4 pages, 2 figures, 2 table
Accessing the Acceleration of the Universe with Sunyaev-Zel'dovich and X-ray Data from Galaxy Clusters
By using exclusively the Sunyaev-Zel'dovich effect and X-ray surface
brightness data from 25 galaxy clusters in the redshift range 0.023< z < 0.784
we access cosmic acceleration employing a kinematic description. Such result is
fully independent on the validity of any metric gravity theory, the possible
matter-energy contents filling the Universe, as well as on the SNe Ia Hubble
diagram.Comment: 3 pages, 4 figures, To appear in the Proceedings of the Twelfth
Marcel Grossmann Meeting on General Relativit
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