Mathematics – Logic
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003phdt.........3z&link_type=abstract
Thesis (PhD). THE OHIO STATE UNIVERSITY, Source DAI-B 64/06, p. 2717, Dec 2003, 273 pages.
Mathematics
Logic
1
Scientific paper
Improvements in observational techniques have transformed cosmology into a field inundated with ever-expanding, high-quality data sets and driven cosmology toward a standard model where the classic cosmological parameters are accurately measured. I briefly discuss some of the methods used to determine cosmological parameters, particularly primordial nucleosynthesis, the magnitude- redshift relation of supernovae, and cosmic microwave background anisotropy. I demonstrate how cosmological data can be used to complement particle physics and constrain extensions to the Standard Model. Specifically, I present bounds on light particle species and the properties of unstable, weakly-interacting, massive particles. Despite the myriad successes of the emerging standard cosmological model, unanswered questions linger. Numerical simulations of structure formation predict galactic central densities that are considerably higher than observed. They also reveal hundreds of satellites orbiting Milky Way-like galaxies while the Milky Way has only eleven known satellites within 300 kpc. I explore the possibility that these conundrums may have a common remedy in the form of the power spectrum of initial density fluctuations that seed structure growth. To address the substructure issue, I develop a semi-analytic method that suffers from no inherent resolution limits and can therefore be used to complement numerical simulations. I find that tilted initial power spectra and spectra with running tilts provide for an intriguing possibility. In these models, the amplitude of initial fluctuations can be normalized against cosmic microwave background measurements on large scales. Yet, the reduction in small-scale power brings galactic central densities down to acceptable levels and allows the Milky Way satellite population to be accounted for without invoking differential feedback mechanisms. Furthermore, substructure mass fractions are not significantly altered in these models so probes of substructure via gravitational lensing do not disfavor them. The primordial fluctuations are thought to be generated during an early epoch of inflation and one implication is that galaxy properties may convey information about inflation. I also address alternative proposals, such as warm dark matter and broken scale-invariant inflation, in light of lensing probes of substructure and find these models to be disfavored. I close with a few words on refining the model and alternative applications.
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