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 \pm 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 { } ^ { +0.15 } _ { -0.7 } 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 .