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Model independent constraints on the cosmological expansion rate
Stockholm University, Faculty of Science, Department of Physics.
2009 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, Vol. 01, 044- p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2009. Vol. 01, 044- p.
Keyword [en]
classical tests of cosmology, cosmology of theories beyond the SM, supernova type Ia
National Category
Astronomy, Astrophysics and Cosmology
Research subject
URN: urn:nbn:se:su:diva-35754DOI: 10.1088/1475-7516/2009/01/044ISI: 000263824000044ISBN: 1475-7516OAI: diva2:287969
Available from: 2010-01-20 Created: 2010-01-20 Last updated: 2011-05-24Bibliographically approved

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Mörtsell, Edvard
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