67 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
Stability of nonlinear magnetic black holes
We study the stability of static spherically symmetric exact solutions of
Einstein equations coupled with nonlinear electrodynamics, in the magnetic
sector. These solutions satisfy the heuristic model proposed by
Ashtekar-Corichi-Sudarsky for hairy black holes, meaning that the horizon mass
is related to their Arnowitt-Deser-Misner (ADM) mass and to the corresponding
particle-like solution. We test the unstability conjecture that emerges for
hairy black holes and it turned out that it becomes confirmed except for the
Einstein-Born-Infeld solutions.Comment: 7 pages, submitted to Phys. Rev. D.In this version the stability of
the solitonic solutions is addresse
Born-Infeld Cosmologies
We present a model for an inhomogeneous and anisotropic early universe filled
with a nonlinear electromagnetic field of Born-Infeld (BI) type. The effects of
the BI field are compared with the linear case (Maxwell). Since the curvature
invaria nts are well behaved then we conjecture that our model does not present
an initial big bang singularity. The existence of the BI field modifies the
curvature invariants at t=0 as well as sets bounds on the amplitude of the
conformal metric functionComment: 13 pages, latex, 6 eps figure
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