2004/03/09 by Zong-Hong Zhu, Zong‐Hong Zhu, Masa-Katsu Fujimoto +3 · 1 citation
Medicine · Physics and Astronomy · #Astrophysics #Black Holes and Theoretical Physics #Classical mechanics #Cosmology #Cosmology and Gravitation Theories #Dark energy #Friedmann equations #Medicine #Observational cosmology #Observational study #Physics #Relativity and Gravitational Theory #Theoretical physics #astro-ph #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1086/381650
published as Astrophys.J.603:365-370,2004 · 19 pages, 6 figures
openalex publication_date 2004/03/09 · arxiv created 2004/03/10 · arxiv updated 2014/10/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 H 2 = (8π G /3)(ρ + C ρ n ). 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 Ω m of the universe from a combined analysis of these databases. We find that n = 0.06 and Ω m = 0.30 , 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.