Ringing in unison: exploring black hole coalescence with quasinormal modes

Open Access
Author:
Bentivegna, Eloisa
Graduate Program:
Physics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
March 05, 2008
Committee Members:
  • Deirdre Shoemaker, Committee Chair
  • Pablo Laguna, Committee Member
  • Lee S Finn, Committee Member
  • Yousry Azmy, Committee Member
Keywords:
  • Numerical relativity
  • black holes
Abstract:
The computational modeling of systems in the strong-gravity regime of General Relativity and the extraction of a coherent physical picture from the numerical data is a crucial step in the process of detecting and recognizing the theory's imprint on our universe. Obtained and consolidated over the past two years, full 3D simulations of binary black hole systems in vacuum constitute one of the first successful steps in this field, based on the synergy of theoretical modeling, numerical analysis and computer science efforts. This dissertation seeks to model the merger of two coalescing black holes, employing a novel technique consisting of the propagation of a massless scalar field on the spacetime where the coalescence is taking place: the field is evolved on a set of fixed backgrounds, each provided by a spatial hypersurface generated numerically during a binary black hole merger. The scalar field scattered from the merger region exhibits quasinormal ringing once a common apparent horizon surrounds the two black holes. This occurs earlier than the onset of the perturbative regime as measured by the start of the quasinormal ringing in the gravitational waveforms, indicating that previous semianalytical evidence on the early validity of perturbative methods during a black hole merger is indeed correct. The scalar quasinormal frequencies are also used to associate a mass and a spin with each hypersurface: this measure is, within our error bars, compatible with the horizon mass and spin computed from the dynamical horizon framework. The emerging physical picture indicates that the behavior of a scalar field propagating on the spacetime of two merged (i.e., surrounded by a common apparent horizon) black holes is very close to that expected on a Kerr spacetime with mass and spin parameters equal to the mass and spin of the common apparent horizon at the end of the coalescence.