Searches for a Disformal Scalar 2f Clock Signature in GNSS, GPS, and Pulsar-Timing Data

Preprint on a conformal-plus-disformal scalar EFT predicting a 2f harmonic clock signature alongside the usual 1f signal. The paper derives the observable, reports null searches in GNSS, GPS, and pulsar-timing data, and gives an optical-clock projection under stated assumptions. Quantitative bounds are conditional on the scalar field saturating the local dark matter density.