ringdown-calculations

This repository contains a collection of notebooks for black hole perturbation theory calculations in scalar-tensor theories of gravity. These notebooks are adaptable to the study of different back hole spacetimes in different theories.

• Basic-examples: In this folder you can find two basic examples for the application of black hole perturbation theory in GR and Horndeski gravity.

• Testing-speed-gravity: companion notebook to the paper [2301.10272], where we investigate how the speed of gravitational waves can be tested with ringdown observations. We focus on odd parity quasinormal modes of hairy black holes in Horndeski theories.

Summary of contents: This notebook contains all calculations starting from the covariant action to the final Fisher parameter estimation and all details in between (quadratic action, modified Regge-Wheeler equation, scalar hair and other parametrizations, quasinormal mode calculation, construction of waveform with relevant parameters, calculation of SNR and errors, plots).

• Stability-QNMs-SdS-t-dep: companion notebook to the paper [2408.01720], where we investigate the stability and quasinormal modes of black holes with time-dependent scalar hair.

Summary of contents: This notebook contains all calculations starting from the covariant action to the final Fisher parameter estimation and all details in between (background equations of motion, quadratic action, stability conditions, modified Regge-Wheeler equation, WKB quasinormal mode calculation, construction of waveform with relevant parameters, calculation of SNR and errors).

This notebooks make use of the free WKB package in [1904.1033].

• plots-Stability-QNMs-SdS-t-dep: python code for all plots in [2408.01720].

  • Inverting-no-hair-theorems: companion notebooks and precomputed expressions to the paper [2503.05651], where we investigate stealth black holes solutions in cubic/qadratic higher-order scalar-tensor (HOST) theories both at the background and perturbative levels.

If you use resources found here, please cite the repository and the corresponding works. For any questions or suggestions, email me at sergi.sirera-lahoz@port.ac.uk.

These notebooks make use of the computer algebra package xAct, so their correct evaluation requires the prior installation of xAct. Installation files are freely available together with extensive documentation.

To open a notebook, click on "View Raw" file, select all text (Ctrl A), copy it (Ctrl C), paste it (Ctrl V) into an empty Mathematica page and select "Yes" to interpreting the text.