Inflationary Domain Theory II: High-Redshift Structure Formation and Intermediate-Epoch Parameter Space Analysis

In Paper I 1, we introduced Inflationary Domain Theory (IDT), a two-parameter extension of ΛCDM in which epoch-localized energy density contributions modify the expansion history at specific cosmological epochs, achieving ∆AIC =−8.1 relative to ΛCDM. The early domain (zc ∼ 2000, fdom ∼0.035) modifies the matter power spectrum P(k) near matter-radiation equality by shifting the sound horizon and altering the expansion rate during the radiation-to-matter transition. In this paper, we show that with no additional parameters, the early domain predicts a 20–50% enhancement in UV-bright galaxy abundance at z = 10–15, consistent with elevated abundances reported by the James Webb Space Telescope (JWST). This prediction is independent of the late- time dephasing coupling η0 and arises entirely from parameters constrained by CMB and BAO data unconnected to high-redshift galaxy counts. We map the full η0 parameter space: across η0 ∈−0.05,−0.01, ∆AIC ranges from−5.5 to−8.3, with consistent preference over ΛCDM under an updated DES Y3 S8 = 0.776±0.017 prior. We identify a structural cooperation between the two domains: the early domain alone worsens the acoustic angular scale tension from 3.1σto 4.0σ, as the shift in rd without a corresponding adjustment to dA(z∗) overshoots the angular ratio. Both domains are necessary to achieve la consistency. Ly-α forest one-dimensional power spectrum deviations of 4–10% at the matter level are predicted across the η0 range, with the upper range within current systematic uncertainties and testable by DESI. The parameter space itself constitutes the primary result of this work: data prefer active dual-domain configurations, and DESI Ly-α measurements will determine which region of this space is realized.