2008/11/30 by Edvard Mörtsell, Edvard Mortsell, Chris Clarkson · 1 citation
Physics and Astronomy · #Acceleration #Astronomy and Astrophysical Research #Baryon acoustic oscillations #Cosmic background radiation #Cosmic microwave background #Cosmology and Gravitation Theories #Dark energy #Deceleration parameter #Galaxies: Formation, Evolution, Phenomena #Metric expansion of space #Phantom energy #Redshift #Supernova #astro-ph
paper · pdf · doi:10.1088/1475-7516/2009/01/044
22 pages, 13 figures. Matches version accepted for publication in JCAP
arxiv created 2009/01/28 · openalex publication_date 2009/01/29 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We investigate what current cosmological data tells us about the cosmological expansion rate in a model independent way. Specifically, we study if the expansion was decelerating at high redshifts and is accelerating now, without referring to any model for the energy content of the universe, nor to any specific theory of gravity. This differs from most studies of the expansion rate which, e.g., assumes some underlying parameterised model for the dark energy component of the universe. To accomplish this, we have devised a new method to probe the expansion rate without relying on such assumptions. Using only supernova data, we conclude that there is little doubt that the universe has been accelerating at late times. However, contrary to some previous claims, we can not determine if the universe was previously decelerating. For a variety of methods used for constraining the expansion history of the universe, acceleration is detected from supernovae alone at >5σ, regardless of the curvature of the universe. Specifically, using a Taylor expansion of the scale factor, acceleration today is detected at >12σ. If we also include the ratio of the scale of the baryon acoustic oscillations as imprinted in the cosmic microwave background and in the large scale distribution of galaxies, it is evident from the data that the expansion decelerated at high redshifts, but only with the assumption of a flat or negatively curved universe.