2004ApJ...603..365Z -
Astrophys. J., 603, 365-370 (2004/March-2)
Observational constraints on cosmology from the modified Friedmann equation.
ZHU Z.-H., FUJIMOTO M.-K. and HE X.-T.
Abstract (from CDS):
Recent measurements of Type Ia supernovae, as well as other concordant observations, suggest that the expansion of our universe is accelerating. A dark energy component has usually been invoked as the most feasible mechanism for the acceleration. However, effects arising from possible extra dimensions can mimic dark energy through a modified Friedmann equation. In this work, we investigate some observational constraints on a scenario in which this modification is given by H2=(8πG/3)(ρ+Cρn). We mainly focus our attention on the constraints from recent measurements of the dimensionless coordinate distances to Type Ia supernovae and Fanaroff-Riley Type IIb radio galaxies compiled by Daly & Djorgovski and the X-ray gas mass fractions in clusters of galaxies published by Allen et al. We obtain the confidence region on the power index n and the density parameter Ωmof the universe from a combined analysis of these databases. We find that n=0.06+0.22–0.18 and Ωm=0.30+0.02–0.02, at the 95.4% confidence level, which is consistent within the errors with the standard ΛCDM model. These parameter ranges give a universe whose expansion switches from deceleration to acceleration at a redshift between 0.52 to 0.73.
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Journal keyword(s):
Cosmology: Cosmological Parameters - Cosmology: Theory - Cosmology: Distance Scale - Stars: Supernovae: General - X-Rays: Galaxies: Clusters
Simbad objects:
4
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