Numerical Relativity completion and validation of an Effective-One-Body waveform model

Faithful, robust and fast waveform models are of critical importance to gravitational wave (GW) astronomy to allow for accurate and precise detection and analysis of the source. Waveform models based on the Effective-One-Body (EOB) approach have been proven to be very powerful in their ability to combine analytical information from PN theory, gravitational-self-force theory and more, in order to capture the full picture of merging binary systems. Purely analytical EOB models are however still of insufficient quality to be used in the detection and analysis of GW events. This thesis presents an introduction to the solution of this problem: The completion of EOB waveform models through Numerical Relativity (NR), on the example of non-precessing, non-eccentric Binary Black Hole (BBH) systems, utilizing the framework of the TEOB model. Once completed NR is further used to validate the model to ensure it meets the qualitative needs of GW data analysis.

The infrastructure of the TEOB model is introduced and discussed with a strong focus onto analytical flexibilities that can be used to capture missing information from NR waveforms. The analytical flexibilities of the TEOB model are made up of effective parameters that enter the Hamiltonian so as to modify both the orbital part (i.e.~non-spinning) and the spin-orbit interaction between the orbital angular momentum and the black hole spins. The approximation of a quasi-circular inspiral is corrected effectively in the radiation reaction of the system by imposing NR fitted waveform characteristics. The model is completed with a phenomenological template fitted directly to NR to capture the merger and ringdown of the BBH system. In total 154 BBH-NR waveforms are combined to inform the TEOB. An additional 460 waveforms are used to validate the model. These waveforms span over a large part of the parameter space reaching mass-ratios $m_1/m_2\leq 18$ and black hole spins of up to $|\vec{S}_{1,2}|/m^2_{1,2} \leq 0.998$. This calibration process is presented for three, successively improving avatars of the TEOB model. The TEOB avatars discussed in this thesis are: Firstly, TEOBResumS is a model for the dominant, quadrupolar mode; Secondly, TEOBiResum_SM models BBH systems of non-rotating black holes, extending the calibration of the quadrupolar mode to a large set of 9 further subdominant modes; Finally, TEOBiResumS_SM extends the calibration of all but one subdominant mode to the full spin-range available of available NR waveforms. The fully calibrated models are all evaluated against the NR catalog. In many instances the model does not just meet but exceeds the quality demands for application in GW astronomy. 

The talk will be given on Zoom: https://zoom.us/j/9290951953 at 17:00 Israel Time (16:00 CEST).