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Anirban Kopty

Publications and source records attributed to Anirban Kopty.

2 recordsLinked to original sources
arXiv2026

Biases in Tests of General Relativity from Microlensed Gravitational-Wave Signals

Gravitational-wave (GW) observations of compact binary mergers enable precision tests of general relativity (GR) in the strong-field regime, but their reliability depends on accurate waveform modeling. Unmodeled physical effects can induce systematic biases that mimic deviations from GR. Here we study the impact of GW microlensing on standard LIGO-Virgo-KAGRA tests of GR using GW150914-like simulated signals lensed by isolated point-mass objects with masses in the range $10-10^{5}M_\odot$. We perform Bayesian parameter estimation with unlensed waveform templates and quantify biases in parameterized tests, modified dispersion relation tests, the inspiral-merger-ringdown consistency test (IMRCT) and the meta-IMRCT framework. To compare these tests with a common discriminator, we introduce a unified GR-deviation significance statistic based on the GR quantile, applicable to both one- and multi-dimensional deviation parameters. We find that microlensing-induced waveform distortions can produce significant false deviations from GR, reaching $\sim4σ$ in one-dimensional tests and $\sim4.5σ$ in two-dimensional consistency tests, despite the injected signals being fully GR-compatible. These false deviations arise mainly in the wave-optics regime, where diffraction induces frequency-dependent amplitude and phase modulations, while signals in the long-wavelength and geometric-optics regimes remain largely consistent with GR. We also find that the significance of these apparent deviations does not correlate strongly with microlensing detectability as measured by Bayes factors, showing that GR tests probe waveform projections not captured by global lensing diagnostics. Our results establish wave-optics gravitational lensing as an important astrophysical systematic for present and future precision tests of GR and highlight the need to model propagation effects in next-generation GW analyses.

gr-qc↗
arXiv2026

Optimal cross-correlation technique to search for strongly lensed gravitational waves

As the number of detected gravitational wave (GW) events increases with the improved sensitivity of the observatories, detecting strongly lensed pairs of events is becoming a real possibility. Identifying such lensed pairs, however, remains challenging due to the computational cost and/or the reliance on prior knowledge of source parameters in existing methods. This study investigates a novel approach, Optimal Cross-Correlation Analysis for Multiplets (OCCAM), applied to strain data from one or more detectors for Compact Binary Coalescence (CBC) events identified by GW searches, using an optimal, mildly model-dependent, low computation cost approach to identify strongly lensed candidates. This technique efficiently narrows the search space, allowing for more sensitive, but (much) higher latency, algorithms to refine the results further. We demonstrate that our method performs significantly better than other computationally inexpensive methods. In particular, we achieve 97 percent (80 percent) lensed event detection at a pairwise false positive probability of approximately 13 percent (7 percent) for a single detector with LIGO design sensitivity, assuming an SNR greater than or equal to 10 astrophysically motivated lensed and unlensed populations. Thus, this method, using a network of detectors and in conjunction with sky-localisation information, can enormously reduce the false positive probability, making it highly viable to efficiently and quickly search for lensing pairs among thousands of events, including the sub-threshold candidates.

gr-qc↗