Semester

Fall

Date of Graduation

2021

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Physics and Astronomy

Committee Chair

Zachariah Etienne

Committee Co-Chair

Sean McWilliams

Committee Member

Maura McLaughlin

Committee Member

Adam Halasz

Abstract

In this dissertation, we explore the effects of extremely strong gravitational and electro- dynamic fields using the techniques of numerical relativity. We use the existing black hole simulation software in the Einstein Toolkit to compute the spin-up of two initially nonspin- ning black holes as they pass by each other in space. The angular momentum is imparted by the tidal interaction between the two black holes, in a parallel to Earth’s tides, as described by classical mechanics, which also transfer angular momentum between the Earth’s rotation and the Moon’s orbit. The largest observed dimensionless spin observed was 0.20 with an initial boost of 0.78c, and we conclude that higher spin-ups may be possible with larger initial boosts. We also use NRPy+ to generate C code for new simulations. The first two are written as thorns, or modules, for the Einstein Toolkit (ETK). The first is a simple scalar wave solver, which has proven useful as an introduction to NRPy+ for new users who wish to write their own ETK thorns. The second is an open-source alternative to the Kranc-generated WeylScal4, which calculates the Weyl scalars that are needed to extract gravitational wave information from a simulation. We also port GiRaFFE to NRPy+. While this was originally intended to be another ETK thorn, as the project progressed, it ultimately became a stan- dalone simulation. The individual modules of this code also have their own unit tests as an additional validation step. These unit tests also use continuous integration to ensure that bugs are not unknowingly introduced into the code. In the future, this code will be modified to be able to use arbitrary coordinate systems.

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