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Gauge theoretic signal processing. II. Zero-latency whitening for early warning pipelines

James Kennington1,2,*, Joshua Black1,2, Zach Yarbrough3, Yun-Jing Huang1,2, Chad Hanna1,2,4,5, Leo Tsukada6,7, Amanda Baylor8, Olivia Godwin9, Prathamesh Joshi10 et al.

Cody Messick8, Surabhi Sachdev10, and Ron Tapia1,5

  • *Contact author: james.kennington@ligo.org
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Phys. Rev. D 114, 102001 – Published 6 November, 2026

DOI: https://doi.org/10.1103/z82m-glq3

Abstract

Low-latency gravitational-wave search pipelines are essential for providing early warning alerts of multimessenger astrophysical transients. Current production pipelines whiten the incoming data stream using acausal, linear-phase filters, which require a look-ahead data buffer that introduces several seconds of algorithmic latency. Eliminating this latency requires transitioning to causal, minimum-phase whitening filters that use only past data. However, operating causal filters under nonstationary noise requires more than simply substituting the filter type: the drifting power spectral density must be tracked without degrading the matched-filter signal-to-noise ratio, filter updates must preserve the minimum-phase condition, and the altered phase response must be compensated to maintain sky localization accuracy. In paper I of this series, we introduced a gauge theoretic signal processing framework and showed that the minimum-phase connection on the manifold of power spectra provides a geometrically exact update rule for causal filters. In this paper, we validate that framework numerically and operationally, demonstrating that parallel transport along this connection strictly preserves the minimum-phase property while exactly conserving the matched-filter signal-to-noise ratio. We numerically certify the flatness of this connection, demonstrating that the optimal filter is a path-independent state function of the instantaneous noise. Through an injection campaign on O3 data with 15,347 binary black hole signals across the LIGO-Virgo network, we confirm that this zero-look-ahead architecture preserves the detection sensitivity and interdetector timing and phase accuracy of the standard linear-phase baseline. Implementing this framework within the production sgnl matched-filter pipeline reduces the whitening latency by 1.0 second (33%) relative to the standard linear-phase baseline at a 4-second noise estimation cadence, confirmed both in controlled local tests and on live O3 replay data at production scale. Stride reduction experiments demonstrate that up to 91% of the baseline trigger latency can be eliminated with subsecond pipeline cadence.

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Phys. Rev. D 114, 102001– Published 6 November, 2026
  • Received 29 April 2026
  • Accepted 6 October 2026
Article part of CHORUS
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