In a curvature-coupled propagation framework for modified gravity, gravitational-wave lensing in wave optics shows persistent infrared interactions that prevent the amplification factor from approaching unity at zero frequency, requiring an interacting Green function and partial-wave treatment.
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GW231123: Overlapping Gravitational Wave Signals?
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abstract
The recently discovered gravitational wave event GW231123 was interpreted as the merger of two black holes with a total mass of 190-265 $M_\odot$, making it the heaviest such merger detected to date. Whilst much of the post-discovery literature has focused on its astrophysical origins, primary analyses have exhibited considerable discrepancies in the measurement of source properties between waveform models, which cannot reliably be reproduced by simulations. Such discrepancies may arise when an unaccounted overlapping signal is present in the data, or from phenomena that produce similar effects, such as gravitational lensing or overlapping noise artifacts. In this work, we analyse GW231123 using a flexible model that allows for two overlapping signals, and find that it is favoured over the isolated signal model with Bayes factors of $\sim 10^2 - 10^{4}$, depending on the waveform model. These values lie within the top few per cent of the background distribution. Similar effects are not observed in GW190521, another high-mass event. Under the overlapping signals model, discrepancies in the measurement of source properties between waveform models are largely mitigated. We also find that neglecting an additional signal in overlapping-signal data can lead to discrepancies in the estimated source properties resembling those reported in GW231123. Although the overlapping signal model provides a higher Bayesian evidence, the astrophysical prior probability of two short signals overlapping is low. However, we find that the two recovered sources show similar properties. This, taken with the higher evidence of the two signal model, suggests that gravitational lensing may provide an alternative explanation.
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2026 8representative citing papers
Polynomial models for the (2,2) post-merger waveform amplitudes of eccentric non-spinning binary black holes are constructed from numerical-relativity data as functions of symmetric mass ratio and two merger-time dynamical parameters.
A quenched-disorder approach with Schwinger-Keldysh path integrals produces an averaged density matrix for gravitational waves that separates phase-suppressing exponential terms from oscillatory corrections to coherent propagation.
The BB plot is a new diagnostic that links Bayes factors to their expected distributions under competing hypotheses, enabling validation of calculations and low-cost background estimation for model selection in GW studies.
No evidence for core-collapse formed low-spin IMBHs in GWTC-4, with 90% upper limit on merger rate of 0.077 Gpc^{-3} yr^{-1}, low-spin BH mass truncation at 65 solar masses consistent with pair-instability gap lower edge, and high-spin IMBHs from hierarchical mergers.
Orthonormal QNM analysis of GW250114 raises the significance of the first overtone of the ℓ=m=2 mode from 82.5% to 99.9% and detects no significant deviation from Kerr predictions.
Analysis of GW231123 with IMRPhenomXPHM, IMRPhenomXO4a and NRSur7dq4 yields no waveform-independent evidence for polarization birefringence, with 90% upper limits on the derived coefficient of 0.378, 0.097 and 0.273 respectively.
The high mass and high spin magnitudes inferred for GW231123 using NRSur7dq4 are robust to waveform systematics and Gaussian noise.
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Wave-optics gravitational wave lensing in modified gravity
In a curvature-coupled propagation framework for modified gravity, gravitational-wave lensing in wave optics shows persistent infrared interactions that prevent the amplification factor from approaching unity at zero frequency, requiring an interacting Green function and partial-wave treatment.
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Highly eccentric non-spinning binary black hole mergers: quadrupolar post-merger waveforms
Polynomial models for the (2,2) post-merger waveform amplitudes of eccentric non-spinning binary black holes are constructed from numerical-relativity data as functions of symmetric mass ratio and two merger-time dynamical parameters.
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Gravitational-wave lensing beyond rays: a disordered-system approach
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No evidence for core-collapse formed low-spin IMBHs in GWTC-4, with 90% upper limit on merger rate of 0.077 Gpc^{-3} yr^{-1}, low-spin BH mass truncation at 65 solar masses consistent with pair-instability gap lower edge, and high-spin IMBHs from hierarchical mergers.
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Ringdown Analysis of GW250114 with Orthonormal Modes
Orthonormal QNM analysis of GW250114 raises the significance of the first overtone of the ℓ=m=2 mode from 82.5% to 99.9% and detects no significant deviation from Kerr predictions.
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Polarization Birefringence and Waveform Systematics in GW231123
Analysis of GW231123 with IMRPhenomXPHM, IMRPhenomXO4a and NRSur7dq4 yields no waveform-independent evidence for polarization birefringence, with 90% upper limits on the derived coefficient of 0.378, 0.097 and 0.273 respectively.
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The impact of waveform systematics and Gaussian noise on the interpretation of GW231123
The high mass and high spin magnitudes inferred for GW231123 using NRSur7dq4 are robust to waveform systematics and Gaussian noise.