L. V. A. Cunha | Searcharxiv

arXiv2026

On correlated noise in the LIGO-Virgo network: a test of the stochastic gravitational-wave background hypothesis

We revisit the inter-detector cross-correlation criterion used in gravitational-wave validation by extending the analysis of Creswell et al.~\cite{Creswell2017} to nine LIGO--Virgo candidate events from the O2 and O3 observing runs. For each event, we analyze all three detector pairs (H1$\times$L1, H1$\times$V1, L1$\times$V1) and compare the normalized cross-correlation function $C(τ)$ in the event window with an empirical ensemble of $N=200$ surrounding off-source windows, using a band-pass-only pipeline. In 26 of 27 pair-measurements, the event peak is statistically indistinguishable from the corresponding noise ensemble, including all pairs involving the independent Virgo detector. The only exception is GW190412 in the H1$\times$L1 pair. We conclude that the cross-correlation statistic does not provide a robust standalone separation between event and noise. We interpret the persistence of comparable correlation structure in the LIGO--Virgo pairs as evidence that the strain data may contain a continuous correlated physical component, for which a stochastic gravitational-wave background is a plausible candidate.

gr-qc↗

arXiv2026

Maxwell equations in Schwarzschild spacetime for static and freely falling observers

Classical electrodynamics in curved spacetime is formulated within a tetrad-based framework that preserves the direct physical interpretation of the electromagnetic fields measured by an observer. The formalism is applied to Schwarzschild spacetime for two distinct families of observers described in the same coordinate system: static observers and radially free-falling observers. For static observers, Maxwell equations retain their usual spherical structure, while the gravitational field introduces geometrical corrections in the radial and temporal sectors through the metric function. These corrections are interpreted in terms of proper radial distance, proper time, and the radial variation of the lapse function. For radially free-falling observers, additional kinematical contributions arise from the local radial boost relating the free-falling frame to the static one. As a consequence, charge density mixes with radial current, and the electric and magnetic sectors become intertwined in the temporal-radial projections of Maxwell equations, whereas the angular Ampère-Maxwell and Faraday equations retain the same structure found for the static observer. The weak-field and near-horizon regimes are also examined, and the results are discussed through an effective-medium analogy, in which the Schwarzschild geometry behaves as an inhomogeneous geometrical medium at rest for static observers and as a radially moving effective medium in the temporal-radial sector for free-falling observers.

gr-qc↗