The Interior Observer Cosmological Framework: A Black Hole Cosmology with the CMB as Event Horizon Radiation

A cosmological framework proposing that the observable universe exists inside a Schwarzschild black hole, with the cosmic microwave background as interior Hawking radiation. The geometric boost factor γ = √(r_s/l_P) resolves the 30-order-of-magnitude temperature gap. Einstein-Cartan-Holst torsion generates dark energy. Core predictions require zero free parameters: T_CMB = 2.663 K (2.3% error), ρ_Λ = 6.05 × 10⁻²⁷ kg/m³ (1.5% error), a₀ = 1.345 × 10⁻¹⁰ m/s² (12% error), H₀ = 58.4 km/s/Mpc (predicted). Confrontation with DESI DR1 BAO data, with H₀ as a single fitted parameter, yields χ² = 7.57 (AIC = 9.57) versus ΛCDM χ² = 8.83 (AIC = 14.83, three free parameters) — the IO geometric expansion history is statistically preferred. Developed through human-AI collaboration. v3.4 correction note: v3.2 reported χ² = 15.1 at zero free parameters. Paper 3 identified two errors: (1) the Ω_k normalization used a = r_s instead of the correct a = R_U, shifting Ω_k from −0.057 to −0.130; (2) the DESI comparison used D_V/r_d at all redshifts, but data at z ≥ 0.510 reports D_M/r_d. Both errors independently verified by Gemini. Core predictions (T_CMB, ρ_Λ, a₀, γ derivation) are completely unaffected. v3.4 additionally corrected Paper 1 Table 2 values (H₀ 58.5→58.4, Ω_Λ 0.919→0.933) and standardized decimal precision across all constants. See Paper 3 for full correction analysis. Three changes: T_CMB 2.66→2.663, a₀ 1.35→1.345, and the correction note updated from v3.3 to v3.4 with the Table 2 and precision fixes documented. Everything else unchanged and consistent with Paper 3 v1.3. Paper 4 status: All four core predictions from Paper 1 are verified and extended in Paper 4. The ρ_Λ derivation is confirmed via two independent routes, recovering the Barbero-Immirzi parameter γ_BI to 2.9% of the LQG value (25/25 SymPy checks). The MOND scale a₀ = c²/r_s is confirmed as a zero-parameter prediction; the interpolation function μ(a/a₀) is identified as requiring quantum gravity completion. Paper 1 §6.4's claim that w = −1 is confirmed by CAMB (w = −1/3 ruled out at χ² = 716). Structure formation is proven viable: the OS dust clusters gravitationally, identifying dark matter as the interior geometry itself. The CMB first acoustic peak is predicted at ℓ₁ ≈ 180 (Planck: 220), an 18% tension driven by Ω_m h² = 0.067, which is the framework's most significant open problem. Paper 1 Open Questions #1–5 are all addressed in Paper 4. Companion to Paper 2 (DOI: 10.5281/zenodo.18868612), Paper 3 (DOI: 10.5281/zenodo.18876346), Paper 4 (DOI: 10.5281/zenodo.18883069), Paper 5 (DOI: 10.5281/zenodo.18889865), and Paper 6 (DOI: 10.5281/zenodo.18891475).