The acceleration history of the universe and the properties of the dark energy

Ruth A. Daly, S. G. Djorgovski

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


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 q 0=-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 z T=0.35 -0.7 +0.15 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.

Original languageEnglish (US)
Title of host publicationSUPERNOVA 1987A
Subtitle of host publication20 YEARS AFTER: Supernovae and Gamma-Ray Bursters
Number of pages5
StatePublished - 2007
EventSUPERNOVA 1987A: 20 YEARS AFTER: Supernovae and Gamma-Ray Bursters - Aspen, CO, United States
Duration: Feb 19 2007Feb 23 2007

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


OtherSUPERNOVA 1987A: 20 YEARS AFTER: Supernovae and Gamma-Ray Bursters
Country/TerritoryUnited States
CityAspen, CO

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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