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Tests of Cosmological Structure Growth - Alvise Raccanelli

Cosmology aims to study the origin, composition and evolution of the entire Universe. The standard model for cosmology, called ΛCDM , represents a good fit to most of the observations we have, but it is a phenomenological model with no strong theoretical foundation, so one of the biggest challenges in cosmology (but important for the entire physics) will be to understand if this is the correct model (and so try to find a theoretical framework for it) or if a model with some sort of “new” physics will take place as the standard one. From the theoretical point of view there are several attempts to solve open problems in cosmology, such as the origin of the Universe and the nature of dark energy; their solution could shed some light on profound and interesting questions potentially revolutionising our understanding of nature. Important data revealing the nature of dark energy will be provided by forthcoming and planned galaxy surveys, that will reach a high precision in their measurements. Data available in the next years will allow us to constrain much better the cosmic expansion history, the geometry of the Universe and the growth of structures within it. For this reason, in this thesis we focused on observational tests of one of the key aspects of a cosmological model, the growth of structures; this allowed us to perform tests of cosmological models and General Relativity. We performed studies of the evolution of growth and clustering of cosmological structures and the evolution of the gravitational potential, comparing effects that depend on them against observations coming from various datasets. In particular, in Chapter 2 we test the growth of structures and their clustering using Redshift-Space Distortions (RSD), developing a new methodology to carefully analyse large scale spectroscopic galaxy surveys; we implement and test a practical application of the wide-angle formalism and then we investigate the significance of different systematics that affect measurements of large scale RSD. In Chapter 3 we use the Integrated Sachs-Wolfe (ISW) effect to test cosmological models to search for possible deviations from the ΛCDM model and then to test a model for the evolution of low frequency radio sources. In Chapter 4 we forecast cosmological measurements it will be possible to obtain using forthcoming radio surveys, using different probes such as the auto-correlation of radio sources, the ISW effect, the Cosmic Magnification and a joint analysis, in order to show how they can be used to test deviations from the standard cosmological constant and General Relativity models.
Alvise_Raccanelli_PhD_thesis.pdf8.01 MB