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The Acceleration History of the Universe and the Properties of the Dark Energy

Daly, Ruth A. and Djorgovski, S. G. (2007) The Acceleration History of the Universe and the Properties of the Dark Energy. In: Supernova 1987A: 20 Years after Supernovae and Gamma-Ray Bursters, Aspen, CO, 19-23 February 2007. AIP Conference Proceedings. No.937. American Institute of Physics , Melville, NY, pp. 298-302. ISBN 978-0-7354-0448-9.

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The model-independent method of using type Ia supernovae proposed and developed by Daly & Djorgovski (2003, 2004) has been applied to the Riess et al. (2007) supernovae sample. Assuming only a Robertson-Walker metric, we find q0 = −0.5±0.13, indicating that the universe is accelerating today. This result is purely kinematic, is independent of the contents of the universe, and does not require that a theory of gravity be specified. Our model-independent method allows a determination of q(z) for a particular value of space curvature. When q(z) transitions from negative to positive values, the universe transitions from an accelerating to a decelerating state. For zero space curvature, we find that the universe transitions from acceleration to deceleration at a zedshift of about zT = 0.35<sub>-0.7</sub><sup>+0.15</sup> for the Riess et al. (2007) sample.If a theory of gravity is specified, the supernovae data can be used to determine the pressure, energy density, and equation of state of the dark energy, and the potential and kinetic energy density of a dark energy scalar field as functions of redshift. The relevant equations from General Relativity are applied, and these functions are obtained. The results are consistent with predictions in the standard Lambda Cold Dark Matter model at about the two sigma level.

Item Type:Book Section
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Djorgovski, S. G.0000-0002-0603-3087
Additional Information:© 2007 American Institute of Physics. We would like to thank the observers for their tireless efforts to obtain the supernovae data that makes these studies possible. This work was supported in part by U.S. National Science Foundation grants AST-0507465 (R.A.D.) and AST-0407448 (S.G.D.), and the Ajax Foundation (S.G.D.).
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Ajax FoundationUNSPECIFIED
Subject Keywords:cosmology; supernovae; dark matter
Series Name:AIP Conference Proceedings
Issue or Number:937
Record Number:CaltechAUTHORS:DALaipcp07
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:8999
Deposited By: Archive Administrator
Deposited On:13 Oct 2007
Last Modified:02 Oct 2019 23:56

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