Precise Astronomical Polarization Angle Calibration and its Impact on Studying Lorentz and Parity Violation in the Cosmic Microwave Background
- Author(s): Navaroli, Martin Frank
- Advisor(s): Keating, Brian
- et al.
Precise measurements of the polarization of the Cosmic Microwave Background (CMB) provide a wealth of knowledge regarding fundamental physics and the origins of our universe. We are currently in an era where the CMB polarization B-mode power spectrum is being measured at both small and large angular scales, providing increasingly tighter constraints on both the effects of gravitational lensing and the amount of primordial gravitational waves generated during the epoch of inflation. As we look toward the next generation of ground-based CMB experiments such as the Simons Observatory and CMB-S4, we must further our understanding of the systematic uncertainties that currently limit constraining power on both the tensor-to-scalar ratio and searches for exotic new physics.
Lorentz and parity violating physics such as cosmic birefringence have the effect of rotating the polarization of CMB photons as they traverse cosmological distances, generating B-mode polarization signal and non-zero correlations between the CMB temperature and B-mode power spectra as well as the CMB E-mode and B-mode power spectra, both of which are disallowed by the current standard model of cosmology. This cosmic polarization rotation (CPR) is degenerate with an overall detector misalignment of similar angle magnitude. The precision with which current state-of-the-art polarization calibrators are characterized is presently inadequate to allow for meaningful detections of non-zero CPR from physics that diverge from the standard model to be claimed.
This dissertation provides an overview of the current CMB polarization calibration standards and methodology in the context of the POLARBEAR-1 and Simons Array experiments, as well as the design and characterization of a novel ground-based absolute polarization calibrator that will enable new searches for Lorentz and parity violating physics. The calibrator's repeatability between calibrations scans was proven to better than 0.1 degrees, and results from calibration performed on the POLARBEAR-1 telescope and the POLARBEAR-2b receiver are presented in this work.