Wave-optics gravitational wave lensing in modified gravity
Abstract
We initiate the study of gravitational-wave lensing in the wave-optics regime within modified gravity. We consider a phenomenological setup in which the gravitational-wave amplitude obeys a curvature-coupled propagation equation. This framework reproduces the standard GR behaviour in the geometric-optics regime, while leading to qualitatively different infrared dynamics. In particular, the usual argument implying that the amplification factor approaches unity in the zero-frequency limit no longer applies. This is due to the persistence of curvature-induced interactions in the infrared, which modify the natural propagation basis itself. As a result, the standard Fresnel treatment ceases to be valid at sufficiently low frequency. The correct infrared regime is instead controlled by an interacting static Green function, with a finite-frequency completion provided by a partial-wave formulation. We show that this structure admits an equivalent distorted-wave interpretation, in which the curvature interaction is absorbed into a dressed reference propagation basis, while the residual lensing effect is encoded in finite-frequency phase shifts. We further demonstrate that these phenomena admit a natural interpretation in the language of scattering amplitudes. Wave-optics lensing can therefore probe propagation-level departures from GR that remain entirely invisible in geometric optics.
Versions
Related
- A universal connection between lens density profiles and low-frequency wave optics in gravitational-wave lensing
- Three-dimensional wave optics for weak-field lensing of gravitational waves
- Modeling Uncertainties in Modified Gravity Predictions for the Stochastic Gravitational-Wave Background
- Probing modified gravity with galaxy-cluster-lensed gravitational-wave time delays: impact of systematic effects
- An empirically constrained Covariant Modified Gravity: exact reconstruction of galactic rotation curves and lensing
BibTeX
@misc{garoffolo2026waveoptics,
title = {{Wave-optics gravitational wave lensing in modified gravity}},
author = {Alice Garoffolo and Gianmassimo Tasinato},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2605.21584},
eprint = {2605.21584},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.21584},
}
RIS
TY - UNPB
TI - Wave-optics gravitational wave lensing in modified gravity
AU - Alice Garoffolo
AU - Gianmassimo Tasinato
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2605.21584
UR - https://arxiv.org/abs/2605.21584
AB - We initiate the study of gravitational-wave lensing in the wave-optics regime within modified gravity. We consider a phenomenological setup in which the gravitational-wave amplitude obeys a curvature-coupled propagation equation. This framework reproduces the standard GR behaviour in the geometric-optics regime, while leading to qualitatively different infrared dynamics. In particular, the usual argument implying that the amplification factor approaches unity in the zero-frequency limit no longer applies. This is due to the persistence of curvature-induced interactions in the infrared, which modify the natural propagation basis itself. As a result, the standard Fresnel treatment ceases to be valid at sufficiently low frequency. The correct infrared regime is instead controlled by an interacting static Green function, with a finite-frequency completion provided by a partial-wave formulation. We show that this structure admits an equivalent distorted-wave interpretation, in which the curvature interaction is absorbed into a dressed reference propagation basis, while the residual lensing effect is encoded in finite-frequency phase shifts. We further demonstrate that these phenomena admit a natural interpretation in the language of scattering amplitudes. Wave-optics lensing can therefore probe propagation-level departures from GR that remain entirely invisible in geometric optics.
ER -