Item Details

title

EXTRACTING INFORMATION FROM BLACK HOLE MERGER SIMULATIONS: THE ROBUSTNESS OF QUASINORMAL MODES

author

Gao, Leda

abstract

The final stage of binary black hole (BBH) coalescence, known as the ringdown, results in the formation of a remnant Kerr black hole. According to linear perturbation theory in general relativity (GR), a certain period of the ringdown gravitational-wave (GW) signal emitted by the perturbed Kerr black hole can be described as a superposition of quasinormal modes (QNMs). In GR, the frequencies of these QNMs depend only on the mass and spin of the remnant black hole, embodying the black hole no-hair theorem. This leads to the proposal of testing GR by measuring QNMs in observed ringdown signals, known as black-hole spectroscopy. Meanwhile, the excitation of these QNMs during the ringdown depends on the properties of the progenitor BBH system. A deeper theoretical understanding of QNM excitation patterns is valuable for various applications, such as constructing surrogate waveform models and more robust black hole spectroscopy tests. One crucial step in this direction is performing ringdown fitting to extract QNM coefficients from numerical relativity (NR) waveforms.In this dissertation, we introduce our ringdown fitting package, KerrRingdown, which has been validated against our collaborators' package, qnmfits. To improve the robustness of extracted QNM coefficients, we developed a greedy approach that iteratively extracts QNM coefficients in order from the least-damped QNMs to higher overtones. We also establish a framework to assess the robustness of QNM coefficients. Within this framework, we not only consider the traditional criterion related to the constancy of a QNM’s expansion coefficient over a time window but also emphasize the importance of consistency across different fitting models. After verifying our greedy approach and robustness criteria on a well-studied NR waveform, we developed a pipeline routine to enable the systematic extraction of robust QNM coefficients from any NR waveform. This pipeline is the first step toward our future goal of mapping QNM coefficients to the parameters of progenitor systems.

subject

gravitational wave

quasinormal modes

ringdown

contributor

Cook, Gregory B. (advisor)

Erway, Jennifer B. (committee member)

Anderson, Paul R. (committee member)

Carlson, Eric D. (committee member)

Salsbury, Jr., Freddie R. (committee member)

date

2025-06-24T08:36:22Z (accessioned)

2025-06-24T08:36:22Z (available)

2025 (issued)

degree

Physics (discipline)

identifier

http://hdl.handle.net/10339/110993 (uri)

language

en (iso)

publisher

Wake Forest University

type

Dissertation