Early stages in cosmic structure formation

Abstract

This thesis investigates the origin and evolution of large scale structure in the universe. We approach these questions from two different angles in two related but independent projects. The outcomes of these two investigations jointly contribute to our understanding of the large scale structure of the universe because the structures we see filling our universe today have their origins in the spectrum of density perturbations emerging from the inflationary era. The first project consists of two calculations of the density perturbation spectrum generated by a particular model of inflation called supernatural inflation. We compute the resulting power spectrum from a D numerical simulation and compare it with the predictions of an untested analytic approximation (Randall et al. 1996). We find that the results from these two calculations agree qualitatively. In the second project, using observations of the Lyman-α forest in the spectra of quasars, we characterize the redshift dependence of the flux probability distribution function of the Lyman-α forest in terms of an underlying lognormal model. We find that the lognormal model is good description of the underlying density distribution for redshifts z > 3. Our independent measurements of the optical depth agree with previous standard results.