The Transient Dimensional Transit Model: A Pre-Recombination Energy Injection that Resolves Parameter Tensions and Improves Global Fit by Δχ² = −7.15

This work presents a full global likelihood analysis of the Transient Dimensional Transit Model (DTM), an extension of the baseline model introducing a short-lived early-universe energy injection parameterised by amplitude $A$ and decay scale aca_cac.

The model is implemented within the CLASS Boltzmann solver and evaluated using Planck 2018 CMB (TT, TE, EE, low-ℓ), SDSS DR12 BAO, and Pantheon Type Ia supernova datasets. A maximum-likelihood (MAP) analysis yields a significant improvement over ΛCDM (Δχ² ≈ −7.15), with ΔAIC ≈ −3.15 after accounting for two additional parameters.

The preferred configuration corresponds to an early-time energy enhancement that decays prior to the onset of structure formation, modifying the acoustic regime while preserving late-time cosmology. The improvement is accompanied by a reduction in prior tension, with key parameters, including the Planck calibration parameter and reionisation optical depth returning toward their theoretically expected values.

A residual tension remains in low-ℓ EE polarisation, identified as the primary discriminating observable for future data. The results establish the Transient DTM as a statistically viable extension that improves the global fit at the MAP level and motivates full MCMC posterior analysis to assess parameter constraints and Bayesian evidence.