Citation
Pullen, Anthony Robert (2011) A Survey of Results in Modern Precision Cosmology. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/VJ9N0J70. https://resolver.caltech.edu/CaltechTHESIS:05042011123721947
Abstract
In this work, we evaluate the evidence for some of the more exotic ideas in cosmology for which scientists are searching today, these anomalies being dark matter, statistical anisotropy, and nonGaussianity. Dark matter, which is estimated to comprise 83% of the matter in our universe, still remains undiscovered. We search data from the Energetic Gamma Ray Experiment Telescope for a gammaray line in the energy range 0.110 GeV from the 10X10 degree region around the Galactic center. Our null results lead to upper limits to the line flux from the Galactic center. We use these limits to place constraints on the particle's twophoton annihilation cross section as a function of its mass, which we show to produce stronger limits than those derived from measurements of the 511keV line.
Next, we investigate the possibility that cosmic inflation deviates from statistical isotropy. Statistical isotropy is a common assumption that should be tested. We develop cosmicmicrowavebackground statistics for a directiondependent primordial power spectrum. We then construct minimumvariance estimators for the coefficients of a sphericalharmonic expansion of the directiondependence of the primordial power spectrum. We find that a power quadrupole as small as 2.0% can be detected by the Planck satellite. We also constrain statistical anisotropy of the quadrupolar form using a sample of photometric luminous red galaxies measured by the Sloan Digital Sky Survey. Not detecting evidence, we place limits on an axisymmetric quadrupole model. We find discrepancies between our results and a cosmic microwave background analysis that claimed a positive detection. We also find the quadrupolar asymmetry limits to be between 0.41 and 0.38 with 95% probability.
Finally, we prepare a search for evidence of nonGaussianity in the the early universe. Scaledependent bias has been shown to be a competitive probe of nonGaussianity in largescale structure, and constraints have been calculated using various tracers of the matter distribution. We seek to extend this analysis to the latest sample of photometric quasars measured by the Sloan Digital Sky Survey to search for evidence of scaledependent bias in largescale structure. Specifically we construct three data samples at various redshifts, removing various systematic effects. We calculate the crosscorrelation angular power spectra between two of the data samples to search for any remaining systematics. We find a positive detection on large scales, which leads us to the conclusion that more systematics testing is needed to render this QSO catalog useful to constrain nonGaussianity.
Item Type:  Thesis (Dissertation (Ph.D.)) 

Subject Keywords:  cosmology; dark matter; cosmic microwave background; large scale structure; inflation 
Degree Grantor:  California Institute of Technology 
Division:  Physics, Mathematics and Astronomy 
Major Option:  Physics 
Thesis Availability:  Public (worldwide access) 
Research Advisor(s): 

Group:  TAPIR 
Thesis Committee: 

Defense Date:  26 April 2011 
Record Number:  CaltechTHESIS:05042011123721947 
Persistent URL:  https://resolver.caltech.edu/CaltechTHESIS:05042011123721947 
DOI:  10.7907/VJ9N0J70 
Default Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided. 
ID Code:  6374 
Collection:  CaltechTHESIS 
Deposited By:  Anthony Pullen 
Deposited On:  17 May 2011 23:10 
Last Modified:  26 Oct 2021 17:44 
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