Large-scale structure as a probe of inflation and galaxy formation physics

The distribution of matter on the largest scales and its evolution over time can be used to constrain cosmological models. Comparisons of existing large-scale structure measurements with those of the cosmic microwave background, which probes the Universe at early times, show mild evidence for tension. This tension can potentially be resolved by appealing to extensions of the standard model of cosmology and/or untreated systematic errors in the modelling of LSS, of which baryonic physics has been frequently suggested. We will revisit this tension using carefully calibrated cosmological hydrodynamical simulations, which thus capture the back reaction of the baryons on the total matter distribution. Furthermore, we will extend the BAryons and HAloes of MAssive Systems (BAHAMAS) simulations to assess the impact of uncertainties in the modelling of cosmic inflation. Inflation is an ad hoc addition to the hot big bang model that nicely accounts for many features of the observed Universe, however many of these successes are generic to inflation models of which there are many. Different models predict different amounts of deviation from a powerlaw in the initial power spectrum of density fluctuations. Through direct simulation and comparison to observations, we will provide rigorous constraints on the degree of so-called "running" of the primordial power spectrum spectral index and will assess whether non-standard inflation models can resolve the aforementioned tension.