Speaker: Lucas Lombriser
Location: University of Sussex
Cosmic acceleration may be attributed to a scalar field, which could couple to matter and modify the gravitational interactions. While enhancing gravity on large scales, nonlinear mechanisms such as the chameleon effect can suppress the modification in high-density regions and make it compatible with Solar System tests. The transition between these two regimes provides a unique signature on cluster scales and a great probe of gravity. With special emphasis on f(R) gravity, I present a description of cluster properties in chameleon theories using a mass and environment dependent spherical collapse model. In a second part, I discuss prospects of testing dark energy and modified gravity models at horizon scales using deviations in the galaxy-density field.