Testing Statistical Isotropy in the FRB Sky Distribution: A Selection-Function-Aware Framework

We perform a test of statistical isotropy in the Universe using the sky distribution of fast radio bursts, based on a compilation of $4066$ events detected by multiple surveys. The new analysis still awaits peer review, but it already lays out the central claim clearly.

It matters because astrophysics becomes persuasive only when an observed signal can be tied to a physically defensible explanation. Compact objects such as neutron stars and black holes are natural laboratories for extreme physics, but the distance and complexity of these systems make interpretation difficult without multi-wavelength coverage and careful modeling. A detection without a mechanism is only half a result. the other half comes from showing that the signal fits quantitatively inside a coherent physical picture rather than merely being consistent with a broad family of models. We perform a test of statistical isotropy in the Universe using the sky distribution of fast radio bursts (FRBs), based on a compilation of $4066$ events detected by multiple. Our method is based on the two-point angular correlation function $w(θ)$ as in the Landy--Szalay estimator, together with a tomographic absolute-anisotropy statistic, and.

The significances are obtained from a covariance-aware, SVD-regularized $χ^2$ statistic calibrated empirically against the mock ensemble, and we evaluate four nested scenarios. As for our results, we find that the raw FRB sky is strongly inconsistent with isotropy.

Galactic masking alone reduces the tension by only a factor of $\sim 3$, whereas the selection functions reduce it by nearly four orders of magnitude, showing that the apparent. Only when both effects are combined we obtain that the observed distribution is fully consistent with statistical isotropy.

This result is independently corroborated by the absolute-anisotropy estimator, and is stable under variations of the analysis parameters. Therefore, we find that the FRB sky distribution is consistent with statistical isotropy, helping confirm one of the main predictions of the standard model scenario.

The broader interest lies in turning an observational clue into something that can be weighed against competing models of the underlying physics. Astrophysics does not have the luxury of controlled experiments; everything is inferred from radiation that traveled across cosmic distances under conditions that cannot be reproduced in a terrestrial laboratory. This makes the interpretation chain longer and more uncertain than in bench science, but it also means that a well-constrained measurement of an extreme object carries theoretical information that no earthbound experiment can provide.

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Because this is still a preprint, the result should be read with genuine interest and proportionate caution. Peer review is not a guarantee of correctness, but it is a process that forces authors to respond to technical criticism from specialists who have no stake in a particular outcome. Preprints that survive that process, often with substantive revisions, emerge with a stronger evidential base than the version that first appeared. Until that stage is complete, the responsible reading keeps uncertainty explicitly visible rather than treating the claims as established findings.

The next step is to see whether independent datasets and physical modeling converge on the same interpretation. Multi-wavelength follow-up, combining X-ray, radio and optical data where possible, is typically what separates a compelling detection from a robust physical characterization. In high-energy astrophysics, results that initially looked definitive have been revised when data from a second messenger arrived; the current result should be read with that history in mind. Until peer review and independent follow-up address those open questions, skepticism is not a failure of appreciation for the work; it is part of how science decides what to keep.

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