We present cosmological results from the statistics of lensed quasars in the Sloan Digital Sky Survey ( SDSS ) Quasar Lens Search .
By taking proper account of the selection function , we compute the expected number of quasars lensed by early-type galaxies and their image separation distribution assuming a flat universe , which is then compared with 7 lenses found in the SDSS Data Release 3 to derive constraints on dark energy under strictly controlled criteria .
For a cosmological constant model ( w = -1 ) we obtain \Omega _ { \Lambda } = 0.74 ^ { +0.11 } _ { -0.15 } ( { stat . } ) ^ { +0.13 } _ { -0.06 } ( { syst . } ) .
Allowing w to be a free parameter we find \Omega _ { M } = 0.26 ^ { +0.07 } _ { -0.06 } ( { stat . } ) ^ { +0.03 } _ { -0.05 } ( { syst . } ) and w = -1.1 \pm 0.6 ( { stat . } ) ^ { +0.3 } _ { -0.5 } ( { syst . } ) when combined with the constraint from the measurement of baryon acoustic oscillations in the SDSS luminous red galaxy sample .
Our results are in good agreement with earlier lensing constraints obtained using radio lenses , and provide additional confirmation of the presence of dark energy consistent with a cosmological constant , derived independently of type Ia supernovae .