Is the present expansion of the universe really accelerating?

Abstract

The current observations are usually explained by an accelerating expansion of the present universe. However, with the present quality of the supernovae Ia data, the allowed parameter space is wide enough to accommodate the decelerating models as well. This is shown by considering a particular example of the dark energy equation-of-state $w_{\varphi }\equiv p_{\varphi }/{\rho }_{\varphi }=-1/3$, which is equivalent to modifying the \emph{geometrical curvature} index $k$ of the standard cosmology by shifting it to $(k-\alpha )$ where $\alpha$ is a constant. The resulting decelerating model is consistent with the recent CMB observations made by WMAP, as well as, with the high redshift supernovae Ia data including SN 1997ff at $z=1.755$. It is also consistent with the newly discovered supernovae SN 2002dc at $z=0.475$ and SN 2002dd at $z=0.95$ which have a general tendency to improve the fit.

Replaced with the accepted version to appear in MNRAS

References in corpus (5)

• The Cosmological Constant and Dark Energy
• Cosmological Constant - the Weight of the Vacuum
• The magnification of SN 1997ff, the farthest known Supernova
• Discovery of Two Distant Type Ia Supernovae in the Hubble Deep Field North with the Advanced Camera for Surveys
• Can brane cosmology with a vanishing Λexplain the observations?

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• QSSC re-examined for the newly discovered SNe Ia
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• Einstein-de Sitter model re-examined for the newly discovered SNe Ia
• Modeling Repulsive Gravity with Creation
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• Transition from decelerated to accelerated cosmic expansion in braneworld universes
• Flat Cosmology with Coupled Matter and Dark Energies
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• Do recent supernovae Ia observations tend to rule out all the cosmologies?
• Accelerating Universe from Extra Spatial Dimension
• The possibility of a stable flat dark energy-dominated Swiss-cheese Brane-world universe with a deceleration-acceleration transition