Understanding the cosmic web
  We investigate the characteristics and the time evolution of the cosmic web
from redshift, z=2, to present time, within the framework of the NEXUS+
algorithm. This necessitates the introduction of new analysis tools optimally
suited to describe the very intricate and hierarchical pattern that is the
cosmic web. In particular, we characterize filaments (walls) in terms of their
linear (surface) mass density. This is very good in capturing the evolution of
these structures. At early times the cosmos is dominated by tenuous filaments
and sheets, which, during subsequent evolution, merge together, such that the
present day web is dominated by fewer, but much more massive, structures. We
also show that voids are more naturally described in terms of their boundaries
and not their centres. We illustrate this for void density profiles, which,
when expressed as a function of the distance from void boundary, show a
universal profile in good qualitative agreement with the theoretical
shell-crossing framework of expanding underdense regions.
