The Santiago-Harvard-Edinburgh-Durham void comparison II: unveiling the
  Vainshtein screening using weak lensing
  We study cosmic voids in the normal-branch Dvali-Gabadadze-Porrati (nDGP)
braneworld models, which are representative of a class of modified gravity
theories where deviations from General Relativity are usually hidden by the
Vainshtein screening in high-density environments. This screening is less
efficient away from these environments, which makes voids ideally suited for
testing this class of models. We use N-body simulations of $\Lambda$-cold dark
matter ($\Lambda$CDM) and nGDP universes, where dark matter haloes are
populated with mock galaxies that mimic the clustering and number densities of
the BOSS CMASS galaxy sample. We measure the force, density and weak lensing
profiles around voids identified with six different algorithms. Compared to
$\Lambda$CDM, voids in nDGP are more under-dense due to the action of the fifth
force that arises in these models, which leads to a faster evacuation of matter
from voids. This leaves an imprint on the weak lensing tangential shear profile
around nDGP voids, an effect that is particularly strong for 2D underdensities
that are identified in the plane-of-the-sky. We make predictions for the
feasibility of distinguishing between nDGP and $\Lambda$CDM using void lensing
in upcoming large-scale surveys such as LSST and Euclid. We compare with the
analysis of voids in chameleon gravity theories and find that the weak lensing
signal for 3D voids is similar to nDGP, whereas for 2D voids the differences
with $\Lambda$CDM are much stronger for the chameleon gravity case, a direct
consequence of the different screening mechanisms operating in these theories.
