4,360 research outputs found
Cosmic Acceleration and Anisotropic models with Magnetic field
Plane symmetric cosmological models are investigated with or without any dark
energy components in the field equations. Keeping an eye on the recent
observational constraints concerning the accelerating phase of expansion of the
universe, the role of magnetic field is assessed. In the absence of dark energy
components, magnetic field can favour an accelerating model even if we take a
linear relationship between the directional Hubble parameters. In presence of
dark energy components in the form of a time varying cosmological constant, the
influence of magnetic field is found to be limited.Comment: 19 pages, 3 figures, submitted to EPJ plu
On the Uniqueness of Supersymmetric Attractors
In this paper we discuss the uniqueness of supersymmetric attractors in four
dimensional N=2 supergravity theories coupled to n vector multiplets. We prove
that for a given charge configuration the supersymmetry preserving axion free
attractors are unique. We generalise the analysis to axionic attractors and
state the conditions for uniqueness explicitly. We consider the example of a
two-parameter model and find all solutions to the supersymmetric attractor
equations and discuss their uniqueness.Comment: 12 pages, Late
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