From theory to practice: Reproducibility and Open Science in the CMB field

Abstract

The study of the cosmic microwave background (CMB) radiation is a pillar of modern cosmology that enables us to understand the history, the evolution of structures, and the global shape (topology) of the Universe. This thesis addresses various theoretical, numerical, and observational aspects of this field. On the theoretical side, I extended the current cosmological LCDM standard model by accounting for the effect of high-energetic neutrinos, and I have derived analytical expressions for the gravitational potential in a trigonometric representation for two distinct non-trivial topologies of the Universe. On the numerical side, I have, as a member of the BeyondPlanck collaboration, developed a common computational infrastructure that allows easy installation and deployment of the world's leading code for end-to-end Bayesian CMB analysis called Commander3. We have used this code to reprocess the Planck LFI observations, and our new products represent today the world's cleanest maps of the microwave sky between 30 and 70 GHz. While this code was originally designed to perform massive Monte Carlo sampling, I have modified it to also be able to produce traditional frequentist-style simulations, which is useful for code validation and error propagation purposes for a broad range of current and future CMB experiments.