How to Build a Catalogue of Linearly-Evolving Cosmic Voids
  Cosmic voids provide a powerful probe of the origin and evolution of
structures in the Universe because their dynamics can remain near-linear to the
present day. As a result they have the potential to connect large scale
structure at late times to early-Universe physics. Existing "watershed"-based
algorithms, however, define voids in terms of their morphological properties at
low redshift. The degree to which the resulting regions exhibit linear dynamics
is consequently uncertain, and there is no direct connection to their evolution
from the initial density field. A recent void definition addresses these issues
by considering "anti-halos". This approach consists of inverting the initial
conditions of an $N$-body simulation to swap overdensities and underdensities.
After evolving the pair of initial conditions, anti-halos are defined by the
particles within the inverted simulation that are inside halos in the original
(uninverted) simulation. In this work, we quantify the degree of non-linearity
of both anti-halos and watershed voids using the Zel'dovich approximation. We
find that non-linearities are introduced by voids with radii less than
$5\,\mathrm{Mpc}\,h^{-1}$, and that both anti-halos and watershed voids can be
made into highly linear sets by removing these voids.
