TY - GEN
T1 - The acceleration history of the universe and the properties of the dark energy
AU - Daly, Ruth A.
AU - Djorgovski, S. G.
PY - 2007
Y1 - 2007
N2 - 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.
AB - 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.
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U2 - 10.1063/1.2803581
DO - 10.1063/1.2803581
M3 - Conference contribution
AN - SCOPUS:36849027549
SN - 0735404488
SN - 9780735404489
T3 - AIP Conference Proceedings
SP - 298
EP - 302
BT - SUPERNOVA 1987A
T2 - SUPERNOVA 1987A: 20 YEARS AFTER: Supernovae and Gamma-Ray Bursters
Y2 - 19 February 2007 through 23 February 2007
ER -