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Using Cosmological Observations to Search for New Physics and Study the Structure of the Universe

  • Author(s): Leon, David Anthony
  • Advisor(s): Keating, Brian
  • et al.
Abstract

Cosmological observations have great potential in searching for information about fundamental physics. The large distances and long time scales of distant sources of light allow us to leverage the vastness of the universe to search for tiny deviations to the currently accepted physical laws. This thesis will explore a number of ways that cosmological observations can help us search for new physics and learn about the evolution of the cosmos.

We will examine the dynamics of pseudo-Nambu-Goldstone bosons (PNGBs) and their behavior throughout cosmic history. Quantum scalar fields under the umbrella of PNGBs have been proposed to answer unsolved questions in physics, and they share the characteristic that they could be detected through Lorentz-violating polarization rotation of photons travelling over cosmological distances.

We will then move to a general framework for studying potential Lorentz-violating physics called the Standard Model Extension (SME), and use the framework to place limits on coefficients of the SME. Using wideband optical polarimetry of two active galactic nuclei we demonstrate the ability to place constraints with small aperture telescopes and show how combining multiple simultaneous measurements in adjacent frequency bands increase the constraining power of such observations.

We then probe the evolution of the large scale structure of the universe with a measument of the gravitational lensing deflection power spectrum using measurements of the polarization of the cosmic microwave background (CMB) taken from two years of observations with the POLARBEAR experiment.

And finally we will see how the CMB and other cosmological observations constrain the shape of the primordial power spectrum of scalar perturbations through a likelihood analysis that takes advantage of second order effects in the perturbative expansion of the gravitational metric.

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