qnmfinder

A reverse search algorithm for finding QNMs in the ringdown of NR waveforms that utilizes variable projection for free frequency fits and leverages stable complex amplitudes for constructing a physical ringdown model.

This algorithm was developed for the work presented in arXiv:2503.09678.

A rough schematic of the algorithm can be seen below:

$t_{0}$ is the fitting start time initialized to be some $t_{0}^{f}$, with $t_{0}^{i}$ the earliest fitting start time; $N_{\mathrm{free}}$ is the number of free frequencies used in the VarPro fit initialized to be one; $\Delta t_{0}$ is some amount by which $t_{0}$ is changed after each failed iteration. For more, see build_model.

Installation

After cloning, this package can be installed with

pip install .

Examples and tips

Check out the example in docs/examples/!