7,406 research outputs found
Scalar perturbations and the possible self-destruction of the phantom menace
Some analysis of the supernovae type Ia observational data seems to indicate
that the Universe today is dominated by a phantom field, for which all energy
conditions are violated. Such phantom field may imply a singularity in a future
finite time, called big rip. Studying the evolution of scalar perturbations for
such a field, we show that if the pressure is negative enough, the Universe can
become highly inhomogeneous and this phantom menace may be avoided.Comment: Latex file, 5 page
Gravitational waves in the generalized Chaplygin gas model
The consequences of taking the generalized Chaplygin gas as the dark energy
constituent of the Universe on the gravitational waves are studied and the
spectrum obtained from this model, for the flat case, is analyzed. Besides its
importance for the study of the primordial Universe, the gravitational waves
represent an additional perspective (besides the CMB temperature and
polarization anisotropies) to evaluate the consistence of the different dark
energy models and establish better constraints to their parameters. The
analysis presented here takes this fact into consideration to open one more
perspective of verification of the generalized Chapligin gas model
applicability. Nine particular cases are compared: one where no dark energy is
present; two that simulate the -CDM model; two where the gas acts like
the traditional Chaplygin gas; and four where the dark energy is the
generalized Chaplygin gas. The different spectra permit to distinguish the
-CDM and the Chaplygin gas scenarios.Comment: Latex file, 9 pages, 11 figures eps forma
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