Multiple non-spherical structures from the extrema of Szekeres scalars
  We examine the spatial extrema (local maxima, minima and saddle points) of
the covariant scalars (density, Hubble expansion, spatial curvature and
eigenvalues of the shear and electric Weyl tensors) of the quasi-spherical
Szekeres dust models. Sufficient conditions are obtained for the existence of
distributions of multiple extrema in spatial comoving locations that can be
prescribed through initial conditions. These distributions evolve without shell
crossing singularities at least for ever expanding models (with or without
cosmological constant) in the full evolution range where the models are valid.
By considering the local maxima and minima of the density, our results allow
for setting up elaborated networks of "pancake" shaped evolving cold dark
matter over-densities and density voids whose spatial distribution and
amplitudes can be controlled from initial data compatible with standard early
Universe initial conditions. We believe that these results have an enormous
range of potential application by providing a fully relativistic
non-perturbative coarse grained modelling of cosmic structure at all scales.
