Code to compute self-force inspirals rapidly using the near-identity transformed (NIT’d) equations of motion
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Fast Self-forced Inspirals

Software to rapidly compute inspirals trajectories and their associated waveforms for eccentric small mass-ratio inspirals into a Schwarzschild black hole. The computed inspirals and waveform include local self-force effects.

Details of the near-identity transformation method used can be found in:


The NIT inspiral code depends upon:

Compile the code

Type scons in the main directory to compile.


Running ./NIT_inspiral without any arguments will give a list of the possible arguments. The various options and how to use the code are given below.

Before computing a NIT inspiral you must first compute the the averaged forcing functions. This is performed in two steps:

  1. ./NIT_inspiral -d (to decompose the self-force into Fourier modes)
  2. ./NIT_inspiral -c (to compute the averaged forcing functions from the Fourier coefficients)

A NIT inspiral can now be computed with

./NIT_inspiral -n p0 e0 q

where (p0, e0) are the initial semi-latus rectum and orbital eccentricity and q is the (small) mass ratio. The inspiral is computed from the initial parameters until the onset of plunge near the separatrix. The NIT inspiral will be computed in milliseconds.

A Full self-forced inspiral can be computed with

./NIT_inspiral -f p0 e0 q

This inspiral will take seconds to hours to compute depending on the value of q.

To compute a waveform one must first compute the inspiral using the commands above. The parameters for the waveform (sampling rate etc) are specified in the configuration file found in config/parameters.cfg. To compute the waveform associated with a NIT inspiral use

./NIT -w p0 e0 q -n

Similarly to compute the waveform associated with a full self-forced inspiral use:

./NIT -w p0 e0 q -f


The code is licensed under the GPLv3 (