UC Berkeley

I study various statistical formalisms for estimating anisotropic cosmic birefringence from observations of the cosmic microwave background and propose a new estimator based on observations of the radio emission of distant galaxies. Using existing data, I place constraints on the parameters of a cosmic string network arising from ultralight axions. I also make forecasts of the sensitivity of near-future microwave and radio observations to the anisotropic cosmic birefringence effect. I perform an analysis of the predicted patterns of birefringence due to ultralight axion cosmic strings and demonstrate the power of the scattering transform as a summary statistic that captures the non-Gaussian information in these patterns. If axion cosmic strings are discovered, then this technique can be used to infer the charges of fermions beyond the Standard Model. A method for the simultaneous measurement of cosmic birefringence and cosmic shear is also developed, complementing the standard estimator for cosmic shear due to weak lensing of distant galaxies.