Voids and gravity in the cosmic web Seminar

The gravitational collapse of dark matter on the largest scales in the universe creates a cosmic web of halos, filaments, walls, and voids. These components are primarily distinguished by the dimensionality and dynamics of their collapse. I have developed the ORIGAMI method to identify the cosmic web in cosmological simulations by looking for folds in phase-space, giving a dynamical, parameter-free definition of structures and their boundaries. I will discuss how the ORIGAMI picture of cosmic voids has shown that voids found in the density field are not, contrary to the theoretical expectation, surrounded on all sides by walls and filaments. I will then show how the Vainshtein mechanism, which acts to screen the fifth force in many modified gravity models of cosmic acceleration, depends on the cosmic web morphology of dark matter particles in simulations, independent of density. This result could lead to new tests of gravity in the cosmic web.