Differences with the LAL implementation

The table summarizes some bugs that have been fixed and some improvements introduced in phenomxpy.

We can introduce those fixes in a modified version of lalsuite by activating the LALDict options in the column Name.

Features and Fixes

Name	Model	Description
BugPNAmp (BPN)	THM	Bug in 33 mode 2.5PN amplitude coefficient: -0.086 → -0.86.
BugPI (BPI)	TPHM NNLO, MSA	Missed initialization of powers_of_pi, affecting the L coefficients.
BugWigner5 (BW5)	TPHM	Bug in Wigner coefficients d503, d507: 52.2 → 52.5
BugGammaIntegration (BGI)	TPHM Numerical	When adding the gamma offset, the first element of the array was skipped, causing a discontinuity at the beginning of the waveform.
PhenomT Analytical Derivative (AD)	T*	Replace numerical derivative for computing ansatz coefficients with analytical ones.
NewTimeArray (NTA)	T*	Builds time array as tmin + i * dt. Ensures waveforms with different fmin agree in overlapping regions up to machine precision.
NewRDtimes (NRDT)	TP, TPHM NNLO, MSA	The ringdown attachement started exactly at t=0, but the PN time array might not ended exactly at t=0.
RefAngles (RA)	TP, TPHM NNLO, MSA	The angles at reference time (alphaJtoI, …) where computed from the closest point in the time array to tref. Now it uses exactly tref.

Remaining differences:

• The numerical solving of tmin and tref introduces some error. One can pass tmin, tref from lal to phenomxpy and get much better agreement.

• The high pass filter used for the FFT (taken from gwsignal) can also introduce some small error. In phenomxpy one can set high_pass_filter_lal = True.

Warning

If you build the time array for LAL using the epoch, bear in mind that this only has precision up to nanoseconds. The option use_exact_epoch (EP) uses the epoch up to machine precision by storing tmin in the f0 argument of LALCOMPLEX16TimeSeries and read it from there.