Absence of anti-correlations and of baryon acoustic oscillations in the
  galaxy correlation function from the Sloan Digital Sky Survey DR7
  One of the most striking features predicted by standard models of galaxy
formation is the presence of anti-correlations in the matter distribution at
large enough scales (r>r_c). Simple arguments show that the location of the
length-scale r_c, marking the transition from positive to negative
correlations, is the same for any class of objects as for the full matter
distribution, i.e. it is invariant under biasing. This scale is predicted by
models to be at about the same distance of the scale signaling the baryonic
acoustic oscillation scale r_{bao}. We test these predictions in the newest
SDSS galaxy samples.We find that, in several MG samples, the correlation
function remains positive at scales >250 Mpc/h, while in the concordance LCDM
it should be negative beyond r_c\approx 120 Mpc/h. In other samples the
correlation function becomes negative at scales <50 Mpc/h. To investigate the
origin of these differences we consider in detail the propagation of errors on
the sample density into the estimation of the correlation function. We conclude
that these are important at large enough separations, and that they are
responsible for the observed differences between different estimators and for
the measured sample to sample variations of the correlation function. We
conclude that, in the newest SDSS samples, the large scale behavior of the
galaxy correlation function is affected by intrinsic errors andv
olume-dependent systematic effects which make the detection of correlations to
be only an estimate of a lower limit of their amplitude, spatial extension and
statistical errors. We point out that these results represent an important
challenge to LCDM models as they largely differ from its predictions.(Abridged
version).
