The CMB bispectrum measures three-point correlations in temperature fluctuations. Single-field slow-roll inflation predicts these should be vanishingly small (|f_NL| near zero) and essentially scale-independent. Planck observations show hints of scale-dependent non-Gaussianity, where bispectrum amplitude varies with multipole (Planck 2020; Meerburg 2019). Recovering scale-dependence in inflationary models requires increasingly contrived multi-field potentials.
The standard model assumes single-field slow-roll inflation produces nearly Gaussian primordial perturbations with negligible bispectrum and no significant scale-dependence. Once that origin story is committed to, scale-dependent non-Gaussianity has no place to come from except from baroque inflationary potentials, undermining the elegance inflation was meant to provide.
SCT replaces the hot-dense-center with a superluminal collision and the thermalized debris field. From this single change, primordial perturbations come from a finite multi-stage cascade rather than continuous quantum vacuum fluctuations. The two parent pockets intersected at superluminal v_rel (P22) and dissipated their kinetic energy through roughly N_coll ≈ 10⁴ successive progressively-decelerating collisions (P36, P37) before terminating at sub-luminal velocities (P38) well before t ≈ 1 second (P40).
Central Limit Theorem applied to that finite ensemble of N_coll ≈ 10⁴ events yields a nearly Gaussian random field with corrections of order 1 / √N_coll, naturally producing |f_NL local| ≈ 10⁻² — small but in principle detectable by CMB-S4-class instruments reaching σ(f_NL) ≈ 1. The scale-dependence arises because the cascade has a hierarchy of characteristic length scales, one per cascade generation, rather than a single front thickness. The largest collision stages deposit perturbations on the scale of the parent-pocket overlap volume (Λ_max ≈ 5 Gpc), while each subsequent stage operates on smaller daughter-fragment scales as v_rel decreases.
This produces a bispectrum amplitude that varies smoothly with multipole, peaking near the angular scales corresponding to dominant cascade stages. The Plasma Equivalence Theorem (P29, P30) preserves the bispectrum signature through the post-thermalization evolution to recombination. Scale-dependent f_NL is therefore the predicted SCT signature of finite-cascade origin, not an unexplained anomaly. The same cascade architecture produces the angular-momentum coherence patterns that explain the CMB Axis of Evil (recid 24) and the connected quadrupoles (recid 18).
Detection of |f_NL local| > 5 at greater than 3σ significance would constrain N_coll < 25, conflicting with the roughly 10⁴ events the Gaussian-spectrum derivation requires. Conversely, if f_NL is confirmed to be exactly zero at the 10⁻² level (CMB-S4 + 21-cm joint analysis), the finite-cascade prediction is refuted in favor of strict single-field inflation or an alternative origin.