qnm: A Python package for calculating Kerr quasinormal modes, separation constants, and spherical-spheroidal mixing coefficients

TL;DR

The qnm Python package offers efficient computation of Kerr quasinormal modes, separation constants, and mixing coefficients, facilitating research in black hole physics with optimized algorithms and caching strategies.

Contribution

It introduces a comprehensive Python toolkit with a Leaver solver, spectral angular approach, and caching system for fast, accurate Kerr mode calculations.

Findings

Includes a Leaver solver and spectral angular method.

Provides a large cache of low modes for quick access.

Enables interpolation for initial guesses at new parameters.

Abstract

$\mathtt{qnm}$ is an open-source Python package for computing the Kerr quasinormal mode frequencies, angular separation constants, and spherical-spheroidal mixing coefficients. The $\mathtt{qnm}$ package includes a Leaver solver with the Cook-Zalutskiy spectral approach to the angular sector, and a caching mechanism to avoid repeating calculations. We provide a large cache of low $\ell, m, n$ modes, which can be downloaded and installed with a single function call, and interpolated to provide good initial guess for root-polishing at new values of spin.