Large-Scale Structure Topology in Non-Standard Cosmologies

Abstract

On large scales the distribution of galaxies resembles a vast ‘cosmic web’ of clusters, walls, filaments and voids arranged in an interlocking network. The statistical properties of large-scale structure (LSS) are determined by the initial conditions and subsequent gravitational evolution of the Universe; thus LSS can be studied as a probe of the underlying cosmology. In spite of a fairly poor theoretical foundation, ΛCDM has had fantastic success in explaining several features of our Universe including the general properties of LSS. Several alternatives to ΛCDM have been proposed that modify the properties of the dark sector. In this thesis we study a suite of alternative cosmological models by performing an analysis of LSS in terms of topology. We produce N-body simulations to measure the genus curve and its Hermite spectra, Minkowski Functionals and the skewness. We first study dark matter only simulations over a wide range of redshifts and length scales. We find that Warm Dark Matter cannot be distinguished by topology at the scales we considered. Quintessence changes the redshift evolution of the topology in a characteristically different fashion than ΛCDM. We then study Coupled Dark Energy models where the components of the dark sector are coupled. We find that the coupling strength β affects the topology due to several effects related to changes in fundamental physics. The Hermite spectra and Minkowski Functional analyses provide independent information on changes in topology at different stages of the Universe’s history. We also find the coupling strength affects the topology and linear biasing of the halo distribution. We demonstrate that topology is a powerful tool to discriminate between cosmological models and is sensitive to the parameters of these models. Detecting signatures of non-standard cosmologies is a vital step in clarifying the mystery that surrounds the dark sector of the Universe.