Substrate Theory: Cosmological Evolution of Intrinsic Decoherence and the Universe's Increasing Quantum Capacity Over Cosmic Time

Substrate framework's energy-eigenstate decoherence formula γ_eff = (ΔE/M_Pc²)² × ν_P [1] depends on the energy gap between superposed states, not on cosmological distance directly. But typical ΔE values for thermal modes, particle physics processes, and inflaton field fluctuations are functions of cosmic energy density, which evolves dramatically over cosmic history. This paper develops the cosmological evolution of substrate intrinsic decoherence across the principal epochs:

• Planck era (t ~ 10⁻⁴⁴ s): Substrate framework breaks down; γ formula not applicable.

• Inflation era (ΔE ~ 10¹⁶ GeV): γ ~ 10³⁷ Hz. Catastrophically fast decoherence drives primordial perturbation classicalization — providing the microscopic mechanism for the well-known but mechanistically unexplained quantum-to-classical transition of cosmological perturbations.

• EW epoch (ΔE ~ 100 GeV): γ ~ 10⁹ Hz. Coherence time τ ~ ns; particle physics processes decohere rapidly.

• QCD epoch (ΔE ~ 100 MeV): γ ~ 10³ Hz. τ ~ ms.

• Nucleosynthesis (ΔE ~ MeV): γ ~ 0.1 Hz. τ ~ 10 s.

• Recombination (ΔE ~ 0.3 eV): γ ~ 10⁻¹⁵ Hz. τ ~ 30 Myr, longer than the age of the universe at that time — the threshold at which the universe becomes capable of sustaining cosmologically long quantum coherence.

• Present era (ΔE ~ k_BT_CMB ~ 0.2 meV): γ ~ 10⁻²¹ Hz. τ ~ 30 Gyr, longer than the current age of the universe. Coherent quantum systems can persist for cosmological timescales.

• de Sitter future: Floor of γ set by dark energy; in the limit, decoherence approaches a constant minimum tied to the cosmological constant.

Three principal results:

(i) The decoherence rate has dropped by ~58 orders of magnitude over cosmic history, from γ ~ 10³⁷ Hz at inflation to γ ~ 10⁻²¹ Hz today. The universe has become exponentially more capable of sustaining coherent quantum behavior as it has cooled.

(ii) Coherent quantum behavior is a late-universe phenomenon. Modern quantum-mechanical experiments (atom interferometry, molecular interferometry, atomic clocks, B-meson oscillations) require a low-energy-density universe to operate. They could not have been performed in the radiation-dominated era because thermal energies were too high.

(iii) Substrate framework provides a microscopic mechanism for primordial perturbation classicalization. Inflaton field quantum fluctuations decohered at γ ~ 10³⁷ Hz during inflation, becoming classical perturbations that seeded the large-scale structure observed today. This resolves a long-standing puzzle in cosmology, where the quantum-to-classical transition is traditionally treated as a black box.

Additionally, the cosmological floor on momentum uncertainty Δp_min ≥ ℏH(t)/c evolved from Δp_min ~ M_Pc at Planck era to Δp_min ~ 10⁻⁶¹ kg·m/s today — a quantum bound that has weakened by ~60 orders of magnitude. In the early universe, quantum uncertainty operated at vastly different scales than today.

These results imply that the substrate framework's intrinsic decoherence sector is fundamentally a cosmological history sector: the framework's quantum-mechanical behavior changes character with cosmic epoch. Quantum coherence is not a universal property but rather a feature of low-energy-density universes. The framework's testable predictions in the modern era (thermal molecular interferometry, atomic clocks) are made possible by the universe having sufficiently cooled.

Section II clarifies what does and doesn't depend on cosmic time. Section III develops the cosmological floor evolution. Section IV develops the decoherence rate across cosmic history with a master table. Section V addresses the early universe's rapid classicalization. Section VI addresses the inflation era specifically and primordial perturbations. Section VII addresses the present era. Section VIII addresses the de Sitter future. Section IX synthesizes the cross-epoch comparison of quantum properties. Section X concludes.

Keywords: substrate theory; cosmological decoherence; primordial perturbations; inflation; quantum-to-classical transition; cosmological floor; energy-eigenstate formula; cosmic evolution of quantum capacity.