ITU and Cosmology: A Single-Axiom View of Big Bang, Inflation, Dark Matter, Dark Energy, Hubble/S_8 Tensions, CMB B-modes, Cosmic Horizons, and the 2026-2050 Observational Roadmap

We apply the Information-Theoretic Unification (ITU) framework (Terada 2026, concept DOI 10.5281/zenodo.20109209; current latest Tier 0 v3.0 at 10.5281/zenodo.20200156) to cosmology. This is Tier 1 paper #19, the third paper of Block A (Physics/Math deepening) and the dual specialization of Tier 1 #17 Quantum Gravity (DOI 10.5281/zenodo.20230667) and Tier 1 #18 Black Holes (DOI 10.5281/zenodo.20233070), completing the HORIZON TRIAD with K_cosmic (observer INSIDE the de Sitter horizon). The ITU polytope reaches 19 vertices with Tier 1 #19 attaining degree 18 (new maximum). Pass-1 progress: 134 of 220 phases (60.9 %). Phase 127 establishes the Big Bang ΛCDM framework. Friedmann equations integrate to age 13.80 Gyr (Planck 2018: 13.797 Gyr). Planck 2018 parameters: H_0 = 67.4 km/s/Mpc, Ω_m = 0.315, Ω_Λ = 0.685, σ_8 = 0.811, n_s = 0.965. de Sitter horizon r_dS = 5.37 Gpc, S_dS = 3.31e+122 nats (Gibbons-Hawking). #18 BH and #19 Cosmic are symmetric specializations of K_geom. Phase 128 covers inflation (Guth 1981, Linde 1982). Slow-roll for V = (1/2)m²φ²: n_s = 0.965 matched at φ ≈ 15.11 M_Pl, r ≈ 0.14 (EXCLUDED by BICEP/Keck 2021 r < 0.06). Surviving models: Starobinsky R² (r ≈ 0.003), Higgs inflation, hilltop. CMB acoustic peaks at ℓ = 220, 540, 810, 1140, 1450. Phase 129 covers dark matter and structure. Milky Way rotation: v_solar visible 141.6 km/s, total (visible + NFW halo) 216 km/s ≈ observed 220 km/s. DM candidates span 53 orders of magnitude (fuzzy 10^{-22} eV to MACHO 10^31 eV). Ω_DM = 0.265. S_8 tension Planck 0.834 vs lensing avg 0.773 = 3.69σ. Phase 130 covers dark energy. Type Ia SN at z=0.5: Δμ = 0.39 mag (accelerating expansion, Nobel 2011). Λ problem: theoretical ρ_vac ~10^120 times observed (Weinberg 1989). CKN holographic bound reduces gap to ~10^17. DESI Y1 (2024): w_0 = -0.95, w_a = -0.39 (2-4σ from ΛCDM, evolving DE hint). Phase 131 deepens tensions. Late H_0 73.91 ± 0.90 vs early 67.92 ± 0.30 = Hubble tension 6.30σ. S_8 CMB 0.837 vs lensing 0.773 = 3.69σ. EDE alone worsens S_8; compounded EDE + IDM resolves both simultaneously. ITU K-state superposition naturally accommodates. Phase 132 covers CMB B-mode + LiteBIRD. E-mode acoustic peaks at ℓ~140; B-mode primordial bumps at ℓ~80-100 (recomb) + ℓ~5 (reion); lensing peak ℓ~1000. LiteBIRD (JAXA, 2032 launch) targets r ~ 0.001 (5σ at r ≥ 0.005). CMB-S4 (2030s) targets r ~ 0.0005. r = 0.001 corresponds to V^{1/4} = 5.6e+15 GeV (near GUT scale). Phase 133 covers cosmic horizons + multiverse. Three horizons: particle 46.95 Gly, event 17.53 Gly (= de Sitter), Hubble 14.51 Gly. S_dS = 3.31e+122 nats = observable universe info capacity. Tegmark Level I-IV mapped to ITU K-state realization space; string landscape ~10^500 vacua, 10^377× observable universe info. Anthropic Λ bound (Weinberg 1987) consistent with observation within 10x. Phase 134 integrates under K_cosmic. 19-vertex polytope: 111 edges (93 + 18 new), avg degree 11.68. Tier 1 #19 couples strongly to #17 QG (0.95, parent), #18 BH (0.85, dual), #10 Energy (0.80); average coupling 0.400. HORIZON TRIAD #17 → #18 + #19 forms inside/outside dual specialization pair. Ten falsifiable predictions for 2026-2050: LiteBIRD r ~ 0.001 detected 2034 P=0.85, Hubble >6σ confirmed 2027 P=0.80, DESI evolving DE 2027 P=0.75, S_8 >4σ 2030 P=0.70, CMB-S4 2035 P=0.60, PBH DM 2038 P=0.55, EDE+IDM 2035 P=0.55, anthropic Λ 2040 P=0.45, LiteBIRD τ 2034 P=0.75, multiverse Level II 2050 P=0.30. Grand P_avg = 0.630. Strong/Medium/Weak = 6/3/1. Central thesis: ITU axiom delta S = delta <K> specializes to K_cosmic at cosmological horizons, unifying Big Bang ΛCDM, inflation, DM, DE, Hubble+S_8 tensions, CMB B-modes, multiverse, and holographic information bound under one principle. Block A papers 1-3 (#17 QG + #18 BH + #19 Cosmology) form HORIZON TRIAD covering all spacetime-horizon physics. LiteBIRD (2034) and DESI Y3 (2027) provide strongest near-term tests. Pass-2 (Phase 223) will derive evolving K_Λ(t), K_DM dynamical correction, and Compound EDE+IDM in ITU language. Honest framing: Pass-1 interpretive paper. Numerical results agree with established literature (Friedmann 1922, Hubble 1929, Penzias-Wilson 1965, Guth 1981, Linde 1982, Smoot 1992, Riess 1998, Perlmutter 1999, Planck 2018, KiDS-1000 2021, BICEP/Keck 2021, DESI 2024). No new physical predictions beyond cited works; contribution is unified ITU axiom narrative under K_cosmic and HORIZON TRIAD with #17 and #18. Includes 8 theory documents (theory_phase127-134.md), 8 Python numerical experiments, 8 figures (PNG), 8 JSON summaries. Total runtime ~15 seconds.