The Vainshtein Mechanism in the Cosmic Web
  We investigate the dependence of the Vainshtein screening mechanism on the
cosmic web morphology of both dark matter particles and halos as determined by
ORIGAMI. Unlike chameleon and symmetron screening, which come into effect in
regions of high density, Vainshtein screening instead depends on the
dimensionality of the system, and screened bodies can still feel external
fields. ORIGAMI is well-suited to this problem because it defines morphologies
according to the dimensionality of the collapsing structure and does not depend
on a smoothing scale or density threshold parameter. We find that halo
particles are screened while filament, wall, and void particles are unscreened,
and this is independent of the particle density. However, after separating
halos according to their large scale morphological environment, we find no
difference in the screening properties of halos in filaments versus halos in
clusters. We find that the fifth force enhancement of dark matter particles in
halos is greatest well outside the virial radius. We confirm the theoretical
expectation that even if the internal field is suppressed by the Vainshtein
mechanism, the object still feels the fifth force generated by the external
fields, by measuring peculiar velocities and velocity dispersions of halos.
Finally, we investigate the morphology and gravity model dependence of halo
spins, concentrations, and shapes.
