Cosmic Neutrino Background

The ΛCDM Tension

The Standard Model predicts a Cosmic Neutrino Background (CνB) decoupled at T ~ 1 MeV with T_ν ≈ 1.95 K and N_eff ≈ 3.046. The CMB power spectrum favors the CνB existence via free-streaming signatures, but direct detection remains elusive due to the extremely low energy. BBN and CMB analyses hint at ΔN_eff tensions (some datasets prefer slightly different values), leaving room for non-standard thermal histories or dark radiation (Planck 2018; PTOLEMY 2019).

The ΛCDM Assumption That Creates It

The standard model has CνB production through standard weak-interaction decoupling at T ~ 1 MeV, producing N_eff = 3.046 from three SM neutrino species. Recovering observed N_eff at the per-percent level across BBN + CMB demands precision matching of standard predictions, with any small tensions implying either dark radiation or non-standard neutrino physics.

SCT Resolution: M2 (Plasma Equivalence Theorem)

SCT replaces the hot-dense-center with a superluminal collision and the thermalized debris field. From this single change, the SCT prediction for the CνB is identical to ΛCDM via the Plasma Equivalence Theorem (P29, P30). Cascade termination well before t ≈ 1 second (P40) leaves standard weak-interaction decoupling to proceed at T ~ 1 MeV producing the standard CνB with T_ν ≈ 1.95 K.

Note however the SCT first-principles N_eff prediction of 2.514 ± 0.050 from cascade geometry (paper 4217: SO(3) cascade modes + QCD boundary correction + photon-heating correction) differs from the SM 3.046 (recid 189 cross-link). Under ΛCDM-assumption Planck constraints this creates a 2.8σ open tension; SCT predicts CMB-S4 will discriminate at 17.7σ forecast precision. The SCT-predicted N_eff value reflects the cascade-cascade-mode infrastructure (P22, P23, P36, P40) whose imprint on the relativistic-degree-of-freedom count differs from standard 3-flavor-only weak-decoupling expectations.

Both T_ν ≈ 1.95 K (the temperature, set by standard weak decoupling) and the CνB existence are SCT predictions identical to ΛCDM. Only N_eff differs at the 17.7σ CMB-S4-distinguishable level. PTOLEMY direct-detection of the CνB would test the existence + T_ν predictions at the 10⁻⁴ eV scale equally for both frameworks. Pre-existing matter (P25) supplies the baryon budget for the standard weak decoupling.

Falsifier

If CMB-S4 measures N_eff = 3.046 ± 0.030 cleanly (matching SM-only prediction), the M2 cascade-derived N_eff = 2.514 prediction is refuted at greater than 17.7σ. PTOLEMY non-detection of CνB at predicted T_ν ≈ 1.95 K would refute both ΛCDM and SCT (the prediction is shared).

Premise Grounding

• P22: Physics of superluminal intersections, the cascade-deposition mechanism.
• P23: Collision energy regime, places cascade in the high-energy regime above weak decoupling.
• P25: Pre-existing matter thermalized by collision, supplies the baryon budget.
• P29: Thermodynamic state sufficiency, post-cascade plasma evolution governed by standard physics.
• P30: Six thermodynamic state parameters determine CMB.
• P40: Cascade termination before t ≈ 1 second, weak decoupling proceeds standard.