Clues on void evolution III: Structure and dynamics in void shells
  Inspired on the well known dynamical dichotomy predicted in voids, where some
underdense regions expand whereas others collapse due to overdense surrounding
regions, we explored the interplay between the void inner dynamics and its
large scale environment. The environment is classified depending on its density
as in previous works. We analyse the dynamical properties of void-centered
spherical shells at different void-centric distances depending on this
classification. The above dynamical properties are given by the angular
distribution of the radial velocity field, its smoothness, the field dependence
on the tracer density and shape, and the field departures from linear theory.
We found that the velocity field in expanding voids follows more closely the
linear prediction, with a more smooth velocity field. However when using
velocity tracers with large densities such deviations increase. Voids with
sizes around $18\,h^{-1}\,Mpc$ are in a transition regime between regions with
expansion overpredicted and underpredicted from linear theory. We also found
that velocity smoothness increases as the void radius, indicating the laminar
flow dominates the expansion of larger voids (more than $18\,h^{-1}\,Mpc$). The
correlations observed suggest that nonlinear dynamics of the inner regions of
voids could be dependent on the evolution of the surrounding structures. These
also indicate possible scale couplings between the void inner expansion and the
large scale regions where voids are embedded. These results shed some light to
the origin of nonlinearities in voids, going beyond the fact that voids just
quickly becomes nonlinear as they become emptier.
