Parity symmetry as a diagnostic for spin-precessing binary-black-hole waveform models
Abstract
Parity invariance of general relativity imposes exact relations between waveforms and remnant properties of binary-black-hole configurations related by reversal of the in-plane spins and observer direction. We summarize these relations and construct consistency tests for spin-precessing waveform and remnant models. Applying a conservative, unmaximized overlap diagnostic to seven state-of-the-art waveform models, we find that models built from aligned-spin calibrated waveforms and parity-covariant precession dynamics satisfy the symmetry to numerical precision. The original \texttt{IMRPhenomXO4a} and \texttt{IMRPhenomXPNR} implementations instead exhibit median parity residuals of approximately 1.6×10−3 with broad upper tails, while \texttt{NRSur7dq4} shows its largest violations at high mass ratio and large spin magnitude. The asymmetric extension of \texttt{SEOBNRv5PHM} exhibits a smaller, localized violation, while \texttt{NRSur7dq4Remnant} shows larger residuals in the recoil than in the final mass and spin. We trace these violations to an observer-dependent phase anchor in the \texttt{IMRPhenom} antisymmetric mode, non-invariant parameterization of the \texttt{NRSur7dq4} surrogate fits, and one non-invariant NR-calibrated coefficient in the asymmetric \texttt{SEOBNRv5PHM} extension. Local corrections restore waveform parity to numerical precision for the \texttt{IMRPhenom} and \texttt{SEOBNRv5PHM} cases; restoring it in \texttt{NRSur7dq4} requires refitting the surrogate. Reanalyses of eight GWTC-5.0 events show no qualitative change in astrophysical interpretation, although the \texttt{IMRPhenom} correction yields Jensen-Shannon divergences up to 5×10−2 in individual marginalized posteriors. Exact symmetries thus provide inexpensive, model-independent consistency tests and should be imposed by construction in calibrated waveform models.
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BibTeX
@misc{estelles2026parity,
title = {{Parity symmetry as a diagnostic for spin-precessing binary-black-hole waveform models}},
author = {Héctor Estellés and Sascha Husa and Eleanor Hamilton and Cecilio García-Quirós and Panagiota Kolitsidou and Joan Llobera-Querol},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.10345},
eprint = {2609.10345},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.10345},
}
RIS
TY - UNPB
TI - Parity symmetry as a diagnostic for spin-precessing binary-black-hole waveform models
AU - Héctor Estellés
AU - Sascha Husa
AU - Eleanor Hamilton
AU - Cecilio García-Quirós
AU - Panagiota Kolitsidou
AU - Joan Llobera-Querol
PY - 2026
DA - 2026/09/09
PB - arXiv
DO - 10.48550/arxiv.2609.10345
UR - https://arxiv.org/abs/2609.10345
AB - Parity invariance of general relativity imposes exact relations between waveforms and remnant properties of binary-black-hole configurations related by reversal of the in-plane spins and observer direction. We summarize these relations and construct consistency tests for spin-precessing waveform and remnant models. Applying a conservative, unmaximized overlap diagnostic to seven state-of-the-art waveform models, we find that models built from aligned-spin calibrated waveforms and parity-covariant precession dynamics satisfy the symmetry to numerical precision. The original \texttt{IMRPhenomXO4a} and \texttt{IMRPhenomXPNR} implementations instead exhibit median parity residuals of approximately 1.6×10^−3 with broad upper tails, while \texttt{NRSur7dq4} shows its largest violations at high mass ratio and large spin magnitude. The asymmetric extension of \texttt{SEOBNRv5PHM} exhibits a smaller, localized violation, while \texttt{NRSur7dq4Remnant} shows larger residuals in the recoil than in the final mass and spin. We trace these violations to an observer-dependent phase anchor in the \texttt{IMRPhenom} antisymmetric mode, non-invariant parameterization of the \texttt{NRSur7dq4} surrogate fits, and one non-invariant NR-calibrated coefficient in the asymmetric \texttt{SEOBNRv5PHM} extension. Local corrections restore waveform parity to numerical precision for the \texttt{IMRPhenom} and \texttt{SEOBNRv5PHM} cases; restoring it in \texttt{NRSur7dq4} requires refitting the surrogate. Reanalyses of eight GWTC-5.0 events show no qualitative change in astrophysical interpretation, although the \texttt{IMRPhenom} correction yields Jensen-Shannon divergences up to 5×10^−2 in individual marginalized posteriors. Exact symmetries thus provide inexpensive, model-independent consistency tests and should be imposed by construction in calibrated waveform models.
ER -