CDN-333: The IMF Test — Can a heavier initial mass function close the SLACS mass gap?

CDN-333 sweeps IMF normalisation α from 1.0 (Chabrier) through 1.8 (Salpeter) to 3.0 (super-Salpeter) across all 20 SLACS grade-A strong lenses, self-consistently recomputing g_bar, ν(x), and R_DM at each step. Salpeter reduces R_DM from 0.94 to 0.91 — negligible. The median critical α (where R_DM=0) is 2.58, well beyond any observationally motivated IMF. At α≥2.4, more than a third of lenses become unphysical (f*>1). Verdict: MARGINAL — IMF alone is strained but not excluded. The SLACS mass gap is structural, not a systematic artefact. D13 IMF path closed. CDN-334 pre-registered: adiabatic contraction test. Predecessor: CDN-332 (zenodo.org/records/20775186). Lock: CDN333_IMF_TEST_LOCKED. Art Edition PDF + computation scripts included.