Modeling large scale structure perturbations in the cosmos

Abstract

Discovering the nature and composition of matter and energy in the Universe remains one of cosmology’s most significant challenges. The distribution of these components, particularly dark energy and dark matter—collectively known as the dark sector, which accounts for about 95% of the total energy budget—governs the Universe's evolution. This thesis investigates cosmic perturbations with two key objectives: first, to examine potential anomalies in the standard cosmological model by testing its foundational assumptions, and second, to develop statistical tools to constrain the cosmological parameters of the ΛCDM model. The analysis is divided into two regimes. In the first, we explore perturbations in the linear regime, characterizing early-universe fluctuations and testing a core assumption of the current model—the cosmological principle. In the second regime, we examine perturbations in the mildly non-linear domain, focusing on extracting information from galaxy clustering through the galaxy power spectrum in redshift space. For both investigations, we developed new theoretical and computational tools. In the first, we derived formulas to calculate the fractal dimension of the CMB temperature fluctuation map. In the second, we designed an emulator for the power spectrum multipoles, allowing for faster yet accurate computations.

Date of Award	16 Oct 2024
Original language	English
Awarding Institution	Autonomous University of Barcelona
Sponsors	CSIC - Instituto de Ciencias del Espacio (ICE) & Institut de Ciències del Cosmos, Universitat de Barcelona
Supervisor	Enrique Gaztanaga (Supervisor) & Martin Crocce (Supervisor)