Probing gravity theories beyond general relativity using hydrodynamic N-body simulations

Abstract

For over a hundred years Einstein’s theory of gravity has reigned supreme as the best theory for explaining how gravity functions in our Universe, however during the last 30 years the limitations of the theory have started to become apparent.

If gravity is exclusively governed by Einstein’s theory then the matter and energy of the Universe needs to be dominated by ”dark” components, in order to explain the observed rotational velocity of galaxies and the accelerating expansion of the Universe among others.

One alternative to explain these observational phenomena without the need of ”dark” components is to introduce alternatives to Einstein’s theory. Einstein’s theory is, however, very well tested in our solar system, and any alternative theories must only differ from Einstein’s theory on very large scales, while leaving scales of the order of our solar system identical to Einstein’s theory.

In this dissertation I study the effects that alternative gravity theories, that reduce to Einstein’s theory on small scales, have on the formation of large scale structures in the Universe, with emphasis towards the hydrodynamic gas component of large scale structures that have never before been simulated together with alternative gravity theories. A wide range of characteristic signatures have been identified, and can hopefully be used together with future astronomical observations to test the limits and possibilities of alternative gravity theories.