Reference-Comparison Notes¤

This unlisted page records implementation details behind reference-specific limits. It intentionally excludes run outputs and historical calibration data. For the enforcing thresholds, see Reference Comparisons and Limits.

Frequency-domain comparisons¤

The frequency-domain overlap is a raw same-grid comparison at identical inputs. It is not maximised over time or phase.

IMRPhenomPv2¤

LAL estimates the coalescence-time correction from the derivative of a natural-cubic spline through a small phase grid around ringdown. ripple computes the corresponding derivative directly with JAX autodiff. The resulting time correction can differ near the merger-ringdown feature, appearing as a linear phase ramp rather than an amplitude error. At zero in-plane spin, both implementations remain continuous. IMRPhenomPv2 is nevertheless not required to reduce to IMRPhenomD: its LAL convention swaps the component masses and spins, changing their assignment in asymmetric phase terms.

IMRPhenomXHM¤

The phase of the (3, 2) mode is sensitive to spheroidal-to-spherical mixing near ringdown. The intermediate phase fit is constrained by the phase derivative at the transition, so small differences there can shift the fitted phase. Investigate a discrepancy in this region as a mode-mixing or phase-derivative issue rather than an amplitude discrepancy.

IMRPhenomXP and IMRPhenomXPHM¤

The MSA precession correction is ill-conditioned near angular-momentum resonances, where terms involving d0 + d2 + d4 suffer cancellation. Small float64 differences in spin-evolution coefficients can then be amplified in the precession angles, particularly at high inclination. IMRPhenomXPHM also inherits the (3, 2) mixing sensitivity through its XHM co-precessing seed. The LAL reference explicitly requests PhenomXPrecVersion=222, so an MSA-initialization failure is surfaced rather than silently selecting a different precession approximation.

Continuous-wave comparisons¤

ExactPulsarSignal uses direct LALPulsar building blocks because CWMakeFakeData always includes the Einstein and Shapiro delays that the model intentionally omits. CWMakeFakeData instead provides the end-to-end comparison for the full pulsar models, including detector response, barycentering, and orbital modulation where applicable. That reference path interpolates propagation delays and detector response. A delay error produces a phase error that grows with frequency, so its normalized mismatch has a frequency-squared bound. Detector-response interpolation has a separate amplitude effect, which is covered by the relative-norm bound. The bounds account for those reference approximations; ripple should not reproduce them.