Mapping the anisotropy of a stochastic gravitational wave background: spherical harmonic decomposition

Yu, Jack 2014. Mapping the anisotropy of a stochastic gravitational wave background: spherical harmonic decomposition. MPhil Thesis, Cardiff University. Item availability restricted.

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Abstract

Gravitational wave sources so numerous that they become unresolvable to detectors produce stochastic backgrounds. The Laser Interferometer Space Antenna (LISA) was a proposed space detector. In this thesis, the way with which it can be used to detect gravitational waves is explained. Then, various methods for estimating the anisotropy of a stochastic background are brie y reviewed. Of these, the spherical harmonic decomposition algorithm is implemented to simulate the signal from backgrounds with arbitrary anisotropy, and to compute estimates of a background's anisotropy from data, as well as providing uncertainties of these estimates. The capability of the implementation is demonstrated through the simulation and analysis of of example backgrounds. It is seen that the implementation is able to simulate the signal from a background with the anisotropy of a point source, and recover the anisotropy from simulated signal in the presence of instrumental noise reasonably well. The same thing is also demonstrated for an isotropic background. At a closer look however, it is seen that the overall normalisation of the anisotropy estimates are not consistent with the uncertainty estimates in general. The performance of the implementation is then discussed in the context of the isotropic background. As a step towards resolving this issue, simplified detector responses and noise models are also considered. Several unexplained observations from the simulation of these are described as possible hints for future improvements of the implementation.

Item Type:	Thesis (MPhil)
Status:	Unpublished
Schools:	Physics and Astronomy
Subjects:	Q Science > QB Astronomy
Uncontrolled Keywords:	LISA, gravitational, wave, spherical, harmonics, stochastic, background, anisotropy, anisotropic, multipole, moments, interferometry, space, overlap, reduction, response, time-delay, TDI, unresolvable, cross-correlation, gaussian, stationary, likelihood, estimator, uncertainty, clean, Fisher, matrix, variance, standard, deviation
Funders:	PPARC
Date of First Compliant Deposit:	30 March 2016
Last Modified:	19 Mar 2016 23:37
URI:	https://orca.cardiff.ac.uk/id/eprint/58327

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