A Robust Distance Measurement and Dark Energy Constraints from the
  Spherically-Averaged Correlation Function of Sloan Digital Sky Survey
  Luminous Red Galaxies
  We measure the effective distance to z=0.35, D_V(0.35), from the overall
shape of the spherically-averaged two-point correlation function of the Sloan
Digital Sky Survey (SDSS) Data Release 7 (DR7) luminous red galaxy (LRG)
sample. We find D_V(0.35)=1428_{-73}^{+74} without assuming a dark energy model
or a flat Universe. We find that the derived measurement of
r_s(z_d)/D_V(0.35)=0.1143 \pm 0.0030 (the ratio of the sound horizon at the
drag epoch to the effective distance to z=0.35) is more tightly constrained and
more robust with respect to possible systematic effects. It is also nearly
uncorrelated with \Omega_m h^2.
  Combining our results with the cosmic microwave background and supernova
data, we obtain \Omega_k=-0.0032^{+0.0074}_{-0.0072} and
w=-1.010^{+0.046}_{-0.045} (assuming a constant dark energy equation of state).
By scaling the spherically-averaged correlation function, we find the Hubble
parameter H(0.35)=83^{+13}_{-15} km s^{-1}Mpc^{-1} and the angular diameter
distance D_A(0.35)=1089^{+93}_{-87} Mpc.
  We use LasDamas SDSS mock catalogs to compute the covariance matrix of the
correlation function, and investigate the use of lognormal catalogs as an
alternative. We find that the input correlation function can be accurately
recovered from lognormal catalogs, although they give larger errors on all
scales (especially on small scales) compared to the mock catalogs derived from
cosmological N-body simulations.
