Constraining the Ψ-Field Cosmic Damper: Cosmic Microwave Background and Big Bang Nucleosynthesis Bounds

This paper extends the cosmological analysis of the damped harmonic oscillator scalar field (Ψ-field) to the extreme conditions of the Early Universe, specifically the Radiation Era, Cosmic Microwave Background (CMB), and Big Bang Nucleosynthesis (BBN). Using the fixed structural constants derived from late-time observations (A ≈ 0.25, m ≈ 3.0, H₀ = 67.07 km/s/Mpc, and Ωₘ = 0.3007), we demonstrate that the model exhibits exceptional numerical stability. The system resolves the angular scale of the CMB acoustic peaks (θ_*) with an extraordinary precision deviation of only $0.000457%$ compared to the Planck 2018 data, calibration-fixing the baryon fraction at Ωb = 0.01498. Furthermore, during the first three minutes of the Universe, the field introduces a $4.8%$ acceleration in the expansion rate (Hᵣₐₜᵢₒ = 1.0482), which naturally balances the lower baryon density to yield a primordial Helium-4 mass fraction of $24.94%$ (within $1.78%$ of observational data). Crucially, the reduced baryon density drastically suppresses primordial Lithium-7 production to 0.30 × 10⁻¹⁰, offering a robust and elegant solution to the long-standing cosmological "Lithium Problem" without invoking any extra parameter or fine-tuning.