Variations on the standard model of the universe

Abstract

In the past decade, due to compelling measurements of the angular power spectrum of the cosmic microwave background (CMB) radiation, the large-scale matter distribution, the recent acceleration of the expansion rate of the Universe over cosmic time, and the current expansion rate (the Hubble constant), cosmology has culminated in a standard model of the Universe. By connecting this standard cosmological model with predictive theories of physics we can hope to look for signatures of these theories in the data. Along this line of inquiry we consider in this thesis: (i) the effects on CMB temperature and polarization anisotropies of spatial fluctuations of the fine-structure parameter alpha between causally disconnected regions of the Universe at the time of recombination, (ii) the suppression of the small-scale matter power spectrum due to the decay of charged matter to dark matter prior to recombination, (iii) the consequences of a neutral dark-matter particle with a nonzero electric and/or magnetic dipole moment, (iv) how charged-particles decaying in the early Universe can induce a scale-dependent or 'running' spectral index in the small-scale matter power spectrum and examples of this effect in minimal supersymmetric models in which the lightest neutralino is a viable cold-dark-matter candidate. With improved tests and cross-checks of standard-cosmological-model predictions we can search for anomalies that may reveal the character of the underlying physics. In this direction we propose in this thesis: (v) a new method for removing the effect of gravitational lensing from maps of CMB polarization anisotropies using observations of anisotropies or structures in the cosmic 21-cm radiation, (vi) that measurements of fluctuations in the absorption of CMB photons by hydrogen in the 21-cm line and deuterium in the 92-cm line during the cosmic dark ages could be used to determine the primordial deuterium abundance.