Trace-Sourced Radiation of Fixed-Ambient Normal Graphs: Retarded Massive Propagation, Emission Thresholds, and Source-to-Calibrated-Detector Transfer

This paper develops the source-to-detector description of fixed-ambient normal-graph radiation within the VGM research program. Building on the interferometric response established in Papers XVIII–XX, it derives the incident normal-field amplitude from minimally coupled matter and propagates it into a calibrated detector channel. At the vacuum normal graph, the leading source is the trace of the matter stress tensor. This yields a classical selection rule: traceless matter does not excite the normal field through this leading coupling. For a compact trace source, the analysis derives the retarded massive field, its directional form factor, and the normalized outgoing energy flux. The propagation calculation distinguishes above-threshold radiation from below-threshold evanescent fields. It supplies additive far-field error bounds that remain meaningful at leading source zeros and states the distance, wavelength, and stationarity conditions required for the local wave-zone approximation. A wave-packet formulation gives the radiative energy spectrum and group propagation time. The source analysis includes quadratic scalar harmonics, on-shell overlap conditions, conservation constraints on the trace monopole, and distinct multipole scalings for massive thresholds and the massless low-frequency limit. A compact prescribed-trace benchmark provides an explicit nonzero radiation coefficient and illustrates source-form-factor cancellation. The resulting field is composed with the finite-arm mechanical response and the cavity, feedback, and calibration operators of Papers XIX–XX. This establishes a leading local forward operator from a specified matter trace to a reconstructed interferometric phase, with finite-distance and curvature corrections retained separately. This deposit contains the English manuscript, revised version 1.1 dated 6 November 2026, its XeLaTeX source, and the accompanying Peaceful Civilian Use Licence. Series: VGM Empirical Correspondence, Calibration, and Falsification Series IV — Overall Paper XXI. DOI: https://doi.org/10.5281/zenodo.24023524