PI: Hayley J Macpherson
In cosmology we typically simplify the dynamics of the Universe via the assumption of a homogeneous and isotropic expansion of space-time. While such an assumption is extremely useful and necessary in most application, the dynamics are realistically more complicated. The existence of the large-scale structure of galaxies naturally results in an expansion of space-time which is dependent on both our physical location as well as which direction we observe on the sky. Theoretical descriptions of this complex expansion typically contain far too many degrees of freedom to be useful for observational constraints. These types of inhomogeneity can only be reliably studied in the context of general-relativistic simulations of cosmological structure formation.
In recent work, we explored these theoretical formalisms using numerical simulations which take into account the full complexity of the inhomogeneous expansion of space-time. Using simulations performed on DiRAC systems, we confirmed the simplified `quiet universe’ model as a good description for a realistic inhomogeneous space-time. From these models we were able to reduce the number of degrees of freedom by a factor of two, as well as identify the dominant anisotropic signatures we could hope to detect in future cosmological data.