PhD Thesis Defenses, 2004
Eugene Lim, "Can We See Lorentz-Violating Vector Fields in the CMB?"
July 14, 2004
Online Materials

Scientific Advisor: Sean M. Carroll

We investigate the perturbation theory of a fixed-norm, timelike Lorentz-violating vector field. After consistently quantizing the vector field to put constraints on its parameters, we compute the primordial spectra of perturbations generated by inflation in the presence of this vector field. We find that its perturbations are sourced by the perturbations of the inflaton; without the inflaton perturbation the vector field perturbations decay away leaving no primordial spectra of perturbations. Since the inflaton perturbation does not have a spin-1 component, the vector field generically does not generate any spin-1 "vector-type" perturbations. Nevertheless, it will modify the amplitude of both the spin-0 "scalar-type" and spin-2 "tensor-type" perturbation spectra, leading to violations of the inflationary consistency relationship.

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KICP Members: Sean M. Carroll
KICP Students: Eugene Lim

Takemi Okamoto, "Effects of instrumental noise on CMB lensing reconstruction"
August 11, 2004
Online Materials

Scientific Advisor: Wayne Hu

Gravitational lensing of the cosmic microwave background results in the generation of higher-order correlations, which can be utilized to estimate the distribution of the intervening dark matter. Although techniques for constructing near-optimal estimators exist, an approach that takes issues related instrumental noise into account is necessary for a realistic assessment of the ability of future experiments to reconstruct gravitational lenses. We provide a quadratic estimator based on a likelihood approach that accounts for survey boundaries and inhomogeneous noise, and discuss the practical issues associated with implementing the estimator. We utilize the quadratic estimator to perform a preliminary study of the effects of survey boundaries and correlated noise on the reconstruction of lenses using the microwave background. We find that the presence of boundaries does not increase the bias in the reconstructed maps, and produce direction-dependent correlations between multipole moments separated by the fundamental mode of the region with missing data. We also examine a simple case of striping, and show that the method results in no additional bias. We conclude that the presence of non-ideal experimental noise does not significantly limit the ability to measure gravitational lensing in the cosmic microwave background.

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KICP Members: Wayne Hu
KICP Students: Takemi Okamoto