The Impact of Cross-Covariances Between the CMB and Reconstructed Lensing Power

Weak gravitational lensing of the Cosmic Microwave Background (CMB) changes CMB statistics in a nontrivial way, allowing for reconstruction of the lensing potential and the use of these reconstructed maps in determining cosmological parameters that affect the formation of intervening large-scale structures. Although in principle there are correlations between the primary CMB and the reconstructed lensing potential due to the lensing procedure itself, in practice CMB analyses treat these as negligible when combining these band powers in likelihoods. In this paper we quantify explicitly the impact on parameter constraints due to these cross-covariances between the lensed CMB and reconstructed lensing power, and we compare to the effect of including all lensing-induced non-Gaussian covariances, which have previously shown to impact parameter constraints on the order of 10%. We perform our analysis for a range of experimental setups, scanning over instrumental noise levels of 0.5 to 10.0 $\mu$K-arcmin in temperature assuming fully polarized detectors, and using a fixed beam size of 1.4 arcmin. When the correlations between the lensed CMB and lensing power are neglected, we find that forecasted constraints shift by at most 3% of the error bar for a 6-parameter $\Lambda$CDM model, and for the noise levels considered in this paper. For some of the $\Lambda$CDM extensions considered here, however, these correlations have a nontrivial impact, in some cases more than 10% of the error bar, even for current experimental noise levels.Comment: 14 pages, 6 figure

Vacuum energy for static, cylindrically symmetric systems

In my previous thesis for the Undergraduate Research Scholars program I have calculated, both in terms of the scalar field and in terms of the cylinder kernel, the components of the stress-energy tensor of a quantized scalar field for a static, cylindrically symmetric system in the case of locally flat space. I then took these components and expressed them in terms of the known cylinder kernel in cylindrical coordinates. Using these results, I examine the vacuum energy density and pressure in some detail for several different cylindrically symmetric space-times. Results are presented for point-splitting along the t direction, and also for point-splitting along z. Geometries studied include flat space, a cone with various deficit angles, an infinite wedge, and the infinite-sheeted Sommerfeld-Dowker manifold. For all of these cases, the energy density and three pressure components are given for xi = 1/4 coupling, and the correction terms for other values of xi are given as well

Extensions of the Standard Model with relation to dark matter and flavor structure

There is a great deal of observational evidence now suggesting the existence of dark matter as the major constituent of the matter content in our universe. Its nature and particle content are still a mystery, and proposing suitable models that can explain its properties would be of great value. This dissertation is a study of the phenomenology of dark matter models with a focus on flavor structure and the rich consequences it can have for the dark sector. We give three implementations of flavored dark matter (FDM) and discuss interesting phenomenological and observational consequences of each. The first model contains asymmetric lepton-flavored dark matter alongside a Higgs portal interaction, resulting in destructive interference that significantly weakens constraints from direct detection bounds. The second study implements a model where a present-day FDM relic can be symmetric, even though it was initially produced in the early universe with an asymmetry in each flavor transferred from the Standard Model via its FDM interactions. Finally, we explore a model where asymmetric DM components interacting via a long-range force can combine to form bound states, and the interactions between these components and a dark photon can address several outstanding issues from astrophysical observations.Physic

Static, cylindrical symmetry in general relativity and vacuum energy

In the first section of my research, in analogy with the standard derivation of the spherically symmetric Schwarzschild solution of the Einstein field equations, I find all static, cylindrically symmetric solutions of the Einstein equations for vacuum. These include not only the well known cone solution, which is locally flat, but others in which the metric coefficients are powers of the radial coordinate and the space-time is curved. These solutions appear in the literature, but in different forms, corresponding to different definitions of the radial coordinate. I find expressions for transforming between these different metric forms and examine some special points of interest. I then examine some special cases of non-vacuum solutions of the equations as well. Because all the vacuum solutions are singular on the axis, I match them to interior solutions with nonvanishing energy density and pressure. In addition to the well known cosmic string solution joining on to the cone, we find some numerical solutions that join on to the other exterior solutions. I then consider only a static, flat, cylindrically symmetric space-time. I calculate the components of the stress-energy tensor in terms of the cylinder kernel and its derivatives. The cylinder kernel in cylindrical coordinates has been previously calculated and can be used to find the energy density and pressure on various cylindrical boundaries; future work will include finding these quantities for various cylindrically symmetric geometries

Gravitational Wave Timing Array

We describe the design of a gravitational wave timing array, a novel scheme that can be used to search for low-frequency gravitational waves by monitoring continuous gravitational waves at higher frequencies. We show that observations of gravitational waves produced by Galactic binaries using a space-based detector like LISA provide sensitivity in the nanohertz to microhertz band. While the expected sensitivity of this proposal is not competitive with other methods, it fills a gap in frequency space around the microhertz regime, which is above the range probed by current pulsar timing arrays and below the expected direct frequency coverage of LISA. The low-frequency extension of sensitivity does not require any experimental design change to space-based gravitational wave detectors, and can be achieved with the data products that would already be collected by them.Comment: 18 pages, 6 figures, comments welcom