Thesis (Ph. D.)--Massachusets Institute of Technology (MIT), 2006. / PDF copy of thesis. Includes bibliograpy.

Thesis (M.Sc.)--York University, 2004. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 86-89). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11775

Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references (p. 118-135). Also available via the World Wide Web.

Thesis (Ph.D.)--University of Waikato, 2006. / Includes bibliographical references (leaves 333-336)

Thesis (Ph. D.)--University of Oregon, 2006. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 75-80). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (M.S.)--Baylor University, 2006. / Includes bibliographical references (p. 74-76).

Astronomy with gravitational-wave observations is now a reality. Much of the theoretical research in this field falls under three broad themes: the mathematical description and physical understanding of gravitational radiation and its effects; the construction of accurate and computationally efficient waveform models for astrophysical sources; and the improved statistical analysis of noisy data from interferometric detectors, so as to extract and characterise source signals. The doctoral thesis presented in this dissertation is an investigation of various topics across these themes. Under the first theme, we examine the direct interaction between gravitational waves and electromagnetic fields in a self-contained theoretical study; this is done with a view to understanding the observational implications for highly energetic astrophysical events that radiate in both the gravitational and electromagnetic sectors. We then delve into the second theme of source modelling by developing and implementing an improved waveform model for the extreme-mass-ratio inspirals of stellar-mass compact objects into supermassive black holes, which are an important class of source for future space-based detectors such as the Laser Interferometer Space Antenna. Two separate topics are explored under the third theme of data analysis. We begin with the procedure of searching for gravitational-wave signals in detector data, and propose several combinatorial compression schemes for the large banks of waveform templates that are matched against putative signals, before studying the usefulness of these schemes for accelerating searches. After a gravitational-wave source is detected, the follow-up process is to measure its parameters in detail from the data; this is addressed as we apply the machine-learning technique of Gaussian process regression to gravitational-wave data analysis, and in particular to the formidable problem of parameter estimation for extreme-mass-ratio inspirals.

We implement a model for, and study the effects of, AGN feedback in cosmological hydrodynamical simulations. In our model, black holes form high-density, primordial gas, to imitate the likely channels of black hole formation in the early Universe. We find that a black hole seed mass of 10²⁻³h⁻¹M⊙ is required to produce simulations that match the cosmic star formation rate density, and present-day black hole mass - velocity dispersion and galaxy size - velocity dispersion relations. We therefore suggest that Population III stars can be the progenitors of the super-massive black holes seen today. Using our fiducial model, we run two large simulations ((25h⁻¹ Mpc)³), one with and one without AGN feedback. With these, we follow the population of galaxies that forms across cosmic time, and find that the inclusion of AGN feedback improves the agreement of simulated and observed galaxy properties, such as the mass and luminosity functions. This agreement is best at z = 0, and fairly good out to z = 2-3. Evidence for downsizing in the evolution of galaxies is found, both in the present-day colour-magnitude and [α/Fe]-velocity dispersion relations, and by the fact that high-mass galaxies attain their present-day metallicity earlier and faster than do low-mass ones. With our hydrodynamical simulations, we can also investigate the internal structure of galaxies, and look at the effects of galaxy mergers and AGN feedback on the stellar and gas-phase metallicity gradients of galaxies. Stellar metallicity gradients are found to be sensitive to galaxy mergers, while gas-phase metallicity gradients are more affected by AGN activity. This suggests that simultaneous measurements of these two quantities can help disentangle the actions of mergers and AGN feedback on a galaxy's history. Finally, we develop a new method to identify massive AGN-driven outflows from the most massive simulated galaxy. These events cause the intra-cluster medium to be hotter and more chemically enriched compared to the simulation without AGN feedback, and therefore AGN feedback may be required in order to attain the metallicities observed in clusters.

We consider the stability of black holes within both classical general relativity and the semiclassical thermodynamic description. In particular, we study linearised perturbations and their contribution to the gravitational partition function, addressing technical issues for charged (Reissner-Nordstrom) and rotating (Kerr-AdS) black holes. Exploring the connection between classical and thermodynamic stability, we find classical instabilities of Myers-Perry black holes and bifurcations to new black hole families.

Techniques for numerically constructing initial data in the 3+1 formalism of general relativity (GR) are studied, using the theoretical framework described in Bowen and York (1980), Physical Review D 21(8), 2047-2056. The two main assumptions made are maximal slicing and 3-conformal flatness of the generated spaces. For ease of numerical solution, axisymmetry is also assumed, but all the results should extend without difficulty to the non-axisymmetric case. The numerical code described in this thesis may be used to construct vacuum spaces containing arbitrary numbers of black holes, each with freely specifyable (subject to the axisymmetry assumption) position, mass, linear momentum, and angular momentum. It should be emphasised that the time evolution of these spaces has not yet been attempted. There are two significant innovations in this work: the use of a new boundary condition for the surfaces of the black holes, and the use of multiple coordinate patches in the numerical solution. The new boundary condition studied herein requires the inner boundary of the numerical grid to be a marginally trapped surface. This is in contrast to the approach used in much previous work on this problem area, which requires the constructed spaces to be conformally isometric under a "reflection mapping" which interchanges the interior of a specified black hole with the remainder of the space. The new boundary condition is found to be easy to implement, even for multiple black holes. It may also prove useful in time evolution problems. The coordinate choice scheme introduced in this thesis uses multiple coordinate patches in the numerical solution, each with a coordinate system suited to the local physical symmetries of the region of space it covers. Because each patch need only cover part of the space, the metrics on the individual patches can be kept simple, while the overall patch system still covers a complicated topology. The patches are linked together by interpolation across the interpatch boundaries. Bilinear interpolation suffices to give accuracy comparable with that of common second order difference schemes used in numerical GR. This use of multiple coordinate patches is found to work very well in both one and two black hole models, and should generalise to a wide variety of other numerical GR problems. Patches are also found to be a useful (if somewhat over-general) way of introducing spatially varying grid sizes into the numerical code. However, problems may arise when trying to use multiple patches in time evolution problems, in that the interpatch boundaries must not become spurious generators or reflectors of gravitational radiation, due to the interpolation errors. These problems have not yet been studied. The code described in this thesis is tested against Schwarzschild models and against previously published work using the Bowen and York formalism, reproducing the latter within the limits of error of the codes involved. A number of new spaces containing one and two black holes with linear or angular momentum are also constructed to demonstrate the code, although little analysis of these spaces has yet been done. / Science, Faculty of / Physics and Astronomy, Department of / Graduate