Constraining General Relativity and the neutrino mass with small scale galaxy clustering

This project uses data from galaxy redshift surveys to constrain the growth of cosmic structure, which
can be used to test General Relativity and alternative theories of gravity as well as measure the sum
of the neutrino masses, a fundamental parameter of particle physics.
The clustering of galaxies is one of the most powerful cosmological probes available and the next
generation of galaxy redshift surveys like the Dark Energy Spectroscopic Instrument (DESI) and the
Euclid satellite mission will increase the size of current datasets by an order of magnitude. These
datasets provide fantastic opportunities to learn more about fundamental concepts governing our
Universe, but at the same time pose significant computational and modelling challenges, which
require new and innovative analysis techniques.
Analytic models for galaxy clustering are limited to large (linear) scales, leaving out most of the
cosmological information. Instead of analytic models here we will use N-body simulations to compare
to the observed galaxy clustering. While N-body simulations do allow to access non-linear scales, the
difficulties are the computational cost of running and processing such simulations as well as the
modelling of the galaxy-halo connection. We will explore new models for the galaxy-halo connection
based on the halo occupation distribution (HOD) formalism combined with analytic and emulator
based modeling of galaxy clustering statistics. We will apply this analysis pipeline to the DESI and
Euclid datasets, to constrain cosmological models. Constraints on the galaxy clustering amplitude
contain information on fundamental neutrino physics and constraints form DESI and Euclid are
expected to measure the sum of the neutrino masses and hence the neutrino mass hierarchy within
the next couple of years