The 3.5 keV line, reported in 2014 cluster stacks and Andromeda and read as 7 keV sterile-neutrino decay, has spent a decade deflating: absent in dwarf spheroidals and the Milky Way halo where dark matter signals should be cleanest, unseen by Hitomi in Perseus, excluded across the parameter space by blank-sky analyses, unconfirmed by eROSITA. It joins WIMPs, axions, and collider partners in ΛCDM's inventory of vanished dark matter candidates.
The model requires a dark matter particle, so every unexplained signal becomes a candidate and every null becomes a constraint rather than a verdict. The 3.5 keV episode is the pattern in miniature: an anomaly elevated by need, then dismantled by the very observations that should have strengthened it if dark matter were physical.
SCT removes the candidate at the source: there is no dark matter particle, sterile or otherwise; the gravitational phenomena attributed to it are coherence amplification of baryons (P50, P52, P53, P54). The framework therefore made the call before the data did: no decay line can scale with dark matter column density because there is no decaying column, and the observed pattern, a feature appearing in complex cluster spectra but vanishing in the clean dwarf-spheroidal tests, is precisely the signature of atomic and instrumental residuals rather than particle physics. The deflation of the 3.5 keV line is a registered SCT success of the same kind as the LUX-ZEPLIN and collider nulls.
The episode also illustrates the framework's economy: ΛCDM must adjudicate every such anomaly against an open-ended particle space, while SCT predicts a clean universal null for all decay, annihilation, and scattering signatures, an unhedged stance that each new X-ray mission tests. XRISM's resolved spectroscopy, separating atomic blends from any smooth residual, is exactly the instrument for the final word.
This is the same no-particle corollary behind the WIMP nulls and the Ω_DM/Ω_b identity. There is no need to invoke environment-dependent decay properties to keep a fading candidate alive.
This resolution is developed in Paper 12, From Chaos to Coherent Gravity, with the underlying mechanism in Paper 11, From Chaos to Cosmic Collisions.
The registered kill is absolute: a confirmed dark matter decay line, a 3.5 keV feature (or any other) tracking dark matter column density across clusters, halo, and dwarfs with consistent intensity scaling, would be a particle detection and would falsify SCT's coherence account outright. XRISM resolving a smooth line at the sterile-neutrino energy, irreducible to atomic transitions, in dark-matter-dominated systems is the specific near-term version.