Waveform modelling of Binary Black Holes in the Advanced LIGO era

The 22th July of 2020 Cecilio García Quirós present his thesis: Waveform modelling of Binary Black Holes in the Advanced LIGO era.

The focus of this thesis is the development of accurate and computationally efficient waveform models for the description of the signal of non-precessing and precessing black-hole binary systems detected by the LIGO-Virgo detectors. Waveform models play a key role in the detection and parameter estimation of gravitational wave signals. The more accurate these models are, the more signals can be detected, but even more importantly, inaccuracies in the signal description will lead to systematic errors for the estimated parameters of the source. The models presented in this thesis include the description of several subdominant effects, which were not considered in the studies during the two first observation runs O1 and O2 of the LIGO-Virgo interferometers, but break degeneracies in the signal and generally improve the accuracy of parameter estimation. During the gap between the O2 and O3 runs several research groups have incorporated the most important subdominant harmonics into their models, however we find that the models presented in this thesis improve the accuracy of several of these models and outperform in computational efficiency to all of them. The non-precessing model follows the standard strategy of the phenomenological models of calibrating an analytical ansatz to numerical relativity simulations. I produced a number of these simulations specifically for the calibration of the model placing them strategically in regions of the parameter space poorly populated. I also produced a number of waveforms in the extreme mass ratio limit extending the calibration region of the model from mass ratio 1 to 1000.

On the other hand, the precessing model follows the standard technique of twisting-up a non-precessing model but extended in this case to a model with subdominant harmonics. The evaluation of the models is then accelerated by incorporating the interpolation technique of “multibanding”, originally introduced by Vinciguerra et. al. I have extended this technique, adapted it to the two frequency domain models presented in this thesis, and formulated the technique in a way to make it applicable to any analytical frequency or time domain model.

Author: Cecilio García Quirós
Title: Waveform modelling of Binary Black Holes in the Advanced LIGO era
Director: Dr. Sascha Husa i Dra. Alicia Sintes Olives
Date: 22 July 2020