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Topics in Gravitational-Wave Astronomy


O'Shaughnessy, Richard William (2004) Topics in Gravitational-Wave Astronomy. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/4C1K-VZ17.


Both the Laser Interferometer Gravitational Wave Observatory (LIGO) and the Laser Interferometer Space Antenna (LISA) will over the next decade detect gravitational waves emitted by the motion of compact objects (e.g. black hole and neutron star binaries). This thesis presents methods to improve (i) LIGO detector quality, (ii) our knowledge of waveforms for certain LIGO and LISA sources, and (iii) models for the rate of detectability of a particular LISA source.

1) Plunge of compact object into a supermassive black hole: LISA should detect many inspirals of compact objects into supermassive black holes (~ 10⁵-10⁷ M). Since the inspiral of each compact object terminates shortly after the inspiralling object reaches its last stable orbit, the late-stage inspiral waveform provides insight into the location of the last stable orbit and strong-field relativity. I discovered that while LISA will easily see the overall inspiral (consisting of many cycles before plunge), the present LISA design will just miss detecting the waves emitted from the transition from inspiral to plunge.

2) Scheme to reduce thermoelastic noise in advanced LIGO: After its first upgrade, LIGO will have its sensitivity limited by thermoelastic noise. [Thermoelastic noise occurs because milimeter-scale thermal fluctuations in the mirror bulk expand and contract, causing the mirror surface to shimmer.] The interferometer's sensitivity could be enhanced substantially by reducing thermoelastic noise. In collaboration with Kip Thorne, Erika d'Ambrosio, Sergey Vyatchanin, and Sergey Strigin, I developed a proposal to reduce thermoelastic noise in advanced-LIGO by switching the LIGO cavity optics from simple spherical mirrors to a new, Mexican-hat shape.

3) Geometric-optics-based analysis of stability of symmetric-hyperbolic formulations of Einstein's equations: Einstein's equations must be evolved numerically to predict accurate waveforms for the late stages of binary black hole inspiral and merger. But no matter which representation of Einstein's equations is used, numerical simulations rarely run long. For examle, for first-order symmetric-hyperbolic (FOSH) formulations of Einstein's evolution equations, sometimes exact but unphysical solutions grow so large that the evolution fails. For FOSH formulations, I found easily-understood solutions (wave packets) and used them to predict which formulations will be particularly ill-behaved.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:LIGO; LISA; numerical relativity; symmetric hyperbolic partial differential equation; thermoelastic noise
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Thorne, Kip S.
Group:TAPIR, Astronomy Department, LIGO
Thesis Committee:
  • Thorne, Kip S. (chair)
  • Libbrecht, Kenneth George
  • Lindblom, Lee A.
  • Kamionkowski, Marc P.
  • Phinney, E. Sterl
Defense Date:29 July 2003
Non-Caltech Author Email:richard.oshaughnessy (AT)
Funding AgencyGrant Number
Record Number:CaltechETD:etd-08052003-161044
Persistent URL:
O'Shaughnessy, Richard William0000-0001-5832-8517
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3017
Deposited By: Imported from ETD-db
Deposited On:15 Aug 2003
Last Modified:21 Jan 2021 00:59

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