Clues on void evolution I: Large scale galaxy distributions around voids
  We perform a statistical study focused on void environments. We examine
galaxy density profiles around voids in the SDSS, finding a correlation between
void--centric distance to the shell of maximum density and void radius when a
maximum in overdensity exists. We analyze voids with and without a surrounding
over-dense shell in the SDSS. We find that small voids are more frequently
surrounded by over-dense shells whereas the radial galaxy density profile of
large voids tends to rise smoothly towards the mean galaxy density. We analyse
the fraction of voids surrounded by overdense shells finding a continuous trend
with void radius. The differences between voids with and without an overdense
shell around them can be understood in terms of whether the voids are, on
average, in the process of collapsing or continuing their expansion,
respectively, in agreement with previous theoretical expectations. We use
numerical simulations coupled to semi-analytic models of galaxy formation in
order to test and interpret our results. The very good agreement between the
mock catalog results and the observations provides additional support to the
viability of a LCDM model to reproduce the large scale structure of the
universe as defined by the void network, in a way which has not been analysed
previously.
