35 research outputs found
Testing a DBI model for the unification of dark matter and dark energy with Gamma-Ray Bursts
We study the range of consistency of a model based on a nonlinear scalar
field Dirac-Born-Infeld action for the unification of dark matter and dark
energy using Gamma-Ray Bursts at high-redshifts. We use the sample of 59
high-redshift GRBs reported by Wei (2010), calibrated at low redshifts with the
Union 2 sample of SNe Ia, thus avoiding the circularity problem. In this
analysis, we also include the CMB7-year data and the baryonic acoustic peak
BAO. Besides, it is calculated the parameter of the equation of state , the
deceleration parameter and the redshift of the transition to the
decelerate-accelerated phase .Comment: 6 pages, to appear in Proceedings of Spanish Relativity Meeting 2011
(ERE 2011) held in Madrid, Spai
Observational constraints on the unified dark matter and dark energy model based on the quark bag model
In this work we investigate if a small fraction of quarks and gluons, which
escaped hadronization and survived as a uniformly spread perfect fluid, can
play the role of both dark matter and dark energy. This fluid, as developed in
\citep{Brilenkov}, is characterized by two main parameters: , related to
the amount of quarks and gluons which act as dark matter; and , acting
as the cosmological constant. We explore the feasibility of this model at
cosmological scales using data from type Ia Supernovae (SNeIa), Long Gamma-Ray
Bursts (LGRB) and direct observational Hubble data. We find that: (i) in
general, cannot be constrained by SNeIa data nor by LGRB or H(z) data;
(ii) can be constrained quite well by all three data sets,
contributing with to the energy-matter content; (iii) when a
strong prior on (only) baryonic matter is assumed, the two parameters of the
model are constrained successfully.Comment: 10 pages, 6 figures, 3 table
Bayesian analysis for a class of -attractor inflationary models
We perform a Bayesian study of a generalization of the basic
-attractor T model given by the potential
where is the inflaton field and the parameter corresponds to
the inverse curvature of the scalar manifold in the conformal or superconformal
realizations of the attractor models. Such generalization is characterized by
the power which includes the basic or base model for . Once the priors
for the parameters of the -attractor potential are set by numerical
exploration, we perform the corresponding statistical analysis for the cases
, and derive posteriors. Considering the original
-attractor potential as the base model, we calculate the evidence for
our generalization, and conclude that the model is preferred by the CMB
data. We also present constraints for the parameter . Interestingly,
all the cases studied prefer a specific value for the tensor-to-scalar ratio
given by .Comment: 16 pages, 8 figures, 3 table