The Peak/Dip Picture of the Cosmic Web
  The initial shear field plays a central role in the formation of large-scale
structures, and in shaping the geometry, morphology, and topology of the cosmic
web. We discuss a recent theoretical framework for the shear tensor, termed the
`peak/dip picture', which accounts for the fact that halos/voids may form from
local extrema of the density field - rather than from random spatial positions;
the standard Doroshkevich's formalism is generalized, to include correlations
between the density Hessian and shear field at special points in space around
which halos/voids may form. We then present the `peak/dip excursion-set-based'
algorithm, along with its most recent applications - merging peaks theory with
the standard excursion set approach.
