Mateja Gosenca (Astronomy Centre, School of Mathematical and Physical Sciences, University of Sussex, United Kingdom)
N-body simulations normally use equations of Newtonian dynamics to evolve particles and fields forward in time. On galactic scales and at times late enough for velocities and gradients of fields to be small this turns out to be an extremely good approximation. However, in modified gravity models, at earlier times when neutrinos are relativistic, or on much larger scales, evolving relativistic sources become important. Therefore, nonlinear evolution of cosmic structure requires a more sophisticated modelling of dynamics. We model general relativity numerically with a weak-field approximation, but still allow for large gradients of the fields and relativistic velocities for the particles. This makes the system much more complicated. In this work, we therefore simplify the system by considering a one-dimensional, spherically symmetric setup. Apart from just reducing the complexity, this setup also allows us to model spherically symmetric fluctuations such as a void or a spherical halo.