Growth rate of cosmological perturbations at z ~ 0.1 from a new
  observational test
  Spatial variations in the distribution of galaxy luminosities, estimated from
redshifts as distance proxies, are correlated with the peculiar velocity field.
Comparing these variations with the peculiar velocities inferred from galaxy
redshift surveys is a powerful test of gravity and dark energy theories on
cosmological scales. Using ~ 2 $\times$ 10$^{5}$ galaxies from the SDSS Data
Release 7, we perform this test in the framework of gravitational instability
to estimate the normalized growth rate of density perturbations f$\sigma_{8}$ =
0.37 +/- 0.13 at z ~ 0.1, which is in agreement with the $\Lambda$CDM scenario.
This unique measurement is complementary to those obtained with more
traditional methods, including clustering analysis. The estimated accuracy at z
~ 0.1 is competitive with other methods when applied to similar datasets.
