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 -