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 Title
 Approximate Isometries as an Eigenvalue Problem and Angular Momentum.
 Creator
 Wilder, Shawn M., Beetle, Christopher, Graduate College
 Date Issued
 20130412
 PURL
 http://purl.flvc.org/fcla/dt/3361373
 Subject Headings
 Black holes (Astronomy), Eigenvalues
 Format
 Document (PDF)
 Title
 Exploring the stability of an eigenvalue problem approximation technique used to define the angular momentum of almost spherical black holes.
 Creator
 Wilder, Shawn M., Beetle, Christopher, Graduate College
 Date Issued
 20110408
 PURL
 http://purl.flvc.org/fcla/dt/3164804
 Subject Headings
 Eigenvalues, Black holes (Astronomy), Deformations (Mechanics)
 Format
 Document (PDF)
 Title
 ELLIPTICA: A NEW PSEUDOSPECTRAL CODE FOR THE CONSTRUCTION OF INITIAL DATA.
 Creator
 Rashti, Alireza, Tichy, Wolfgang, Florida Atlantic University, Department of Physics, Charles E. Schmidt College of Science
 Abstract/Description

Unveiling the secrets of gravity necessitates numerical relativity simulations of gravitational systems, as observations made by gravitational wave detectors expect an interpretation. In the other hand, these numerical simulations require physical and constraintsatisfying initial data. Therefore, the accuracy of simulations go hand in hand with the accuracy of initial data. As such, constructing accurate initial data is an indispensable task and it is the very subject of this dissertation....
Show moreUnveiling the secrets of gravity necessitates numerical relativity simulations of gravitational systems, as observations made by gravitational wave detectors expect an interpretation. In the other hand, these numerical simulations require physical and constraintsatisfying initial data. Therefore, the accuracy of simulations go hand in hand with the accuracy of initial data. As such, constructing accurate initial data is an indispensable task and it is the very subject of this dissertation. Here, we present the newly developed pseudospectral code Elliptica, an infrastructure for construction of initial data for various binary and single gravitational systems of all kinds. The elliptic equations under consideration are solved on a single spatial hypersurface of the spacetime manifold. Using coordinate maps, the hypersurface is covered by patches whose boundaries can adapt to the surface of the compact objects. To solve elliptic equations with arbitrary boundary condition, Elliptica deploys a Schur complement domain decomposition method with a direct solver. In this version, we use cubed sphere coordinate maps and the fields are expanded using Chebyshev polynomials of the first kind. Here, we explain the building blocks of Elliptica and the initial data construction algorithm for black holeneutron star binary systems. We perform convergence tests and evolve the data to validate our results. Within our framework, the neutron star can reach spin values close to breakup with arbitrary direction, while the black hole can have arbitrary spin with dimensionless spin magnitude ~ 0.8.
Show less  Date Issued
 2022
 PURL
 http://purl.flvc.org/fau/fd/FA00014006
 Subject Headings
 Gravitational waves, Elliptic functions, Neutron stars, Black holes (Astronomy)
 Format
 Document (PDF)
 Title
 Binary neutron star mergeres: simulations with arbitrarily spinning stars.
 Creator
 Tsatsin, Petr, Marronetti, Pedro, Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

The starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits,...
Show moreThe starting point of any general relativistic numerical simulation is a solution of the Hamiltonian and momentum constraints that (ideally) represents an astrophysically realistic scenario. This dissertation presents a new method to produce initial data sets for binary neutron stars with arbitrary spins and orbital eccentricities. The method only provides approximate solutions to the constraints. However, it was shown that the corresponding constraint violations subside after a few orbits, becoming comparable to those found in evolutions of standard conformally flat, helically symmetric binary initial data. This dissertation presents the first spinning neutron star binary simulations in circular orbits with a orbital eccentricity less then 0.01. The initial data sets corresponding to binaries with spins aligned, zero and antialigned with the orbital angular momentum were evolved in time. These simulations show the orbital “hangup” effect previously seen in binary black holes. Additionally, they show orbital eccentricities that can be up to one order of magnitude smaller than those found in helically symmetric initial sets evolutions.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fau/fd/FA0004067
 Subject Headings
 Astrophysics, Black holes (Astronomy), General relativity (Physics), Gravitational waves, Neutron stars, Particles (Nuclear physics)
 Format
 Document (PDF)
 Title
 Binary black hole mergers: alternatives to standard puncture initial data and the impact on gravitational waveforms.
 Creator
 Reifenberger, George C., Charles E. Schmidt College of Science, Department of Physics
 Abstract/Description

We study the evolution of binary black hole initial data schemes as alternatives to the standard puncture construction. These alternatives are based on postNewtonian expansions that contain realistic gravitational waves. The first scheme is based on a second order postNewtonian expansion in Arnowitt, Deser, and Misner transversetraceless (ADMTT) gauge that has been resummed to approach standard puncture data at the black holes. The other schemes are based on asymptotic matching of the 4...
Show moreWe study the evolution of binary black hole initial data schemes as alternatives to the standard puncture construction. These alternatives are based on postNewtonian expansions that contain realistic gravitational waves. The first scheme is based on a second order postNewtonian expansion in Arnowitt, Deser, and Misner transversetraceless (ADMTT) gauge that has been resummed to approach standard puncture data at the black holes. The other schemes are based on asymptotic matching of the 4metrics of two tidally perturbed Schwarzschild solutions to postNewtonian expansions at different orders. The alternatives are encouraging and lead to quasicircular orbits and show gravitational radiation from the onset, as well as a reduction of spurious radiation. Deficiencies compared to punctures include more eccentricity during inspiral and larger constraint violations, since the alternative data sets only approximate solutions of Einstein's equations.
Show less  Date Issued
 2013
 PURL
 http://purl.flvc.org/fcla/dt/3362577
 Subject Headings
 Black holes (Astronomy), General relativity (Physics), Gravitational waves, Inertia (Mechanics), Mass (Physics), Particles (Nuclear physics)
 Format
 Document (PDF)
 Title
 Towards reading line profiles of BardeenPetterson accretion disks.
 Creator
 Vandernoot, Eric P., Florida Atlantic University, Miller, Warner A.
 Abstract/Description

Images of highly idealized BardeenPetterson accretion disks around Kerr black holes and their generated energy spectra line profiles are created via computer simulations in this work. The line profiles are examined in the relation to the original disk parameters to demonstrate that BardeenPetterson disks can be the source of the spectra we observe, even of actual systems. The challenges in computer programming the simulations and methods to overcome the challenges are discussed in the paper...
Show moreImages of highly idealized BardeenPetterson accretion disks around Kerr black holes and their generated energy spectra line profiles are created via computer simulations in this work. The line profiles are examined in the relation to the original disk parameters to demonstrate that BardeenPetterson disks can be the source of the spectra we observe, even of actual systems. The challenges in computer programming the simulations and methods to overcome the challenges are discussed in the paper. Also discussed are the future work, improvements and intentions for the simulations. Finally, the discussion turns to the usage of indicators in these line profiles to predict parameters of the original disk systems.
Show less  Date Issued
 2005
 PURL
 http://purl.flvc.org/fcla/dt/13287
 Subject Headings
 Black holes (Astronomy), Accretion (Astrophysics), General relativity (Physics), Gravitation, Petterson, Jacobus Antonius,1946
 Format
 Document (PDF)