The High-Coherence Cosmological Limit: An RCD Interpretation of the Big Bang - Radial Coherential Dynamics — Paper XIX

We analyze the cosmological initial-state limit of the P2 action (Paper I) by integrating the coupled Friedmann–Klein-Gordon system from high redshift (z ~ 22,000) to the far future (a ~ 15). The early universe corresponds to the high-coherence limit C → 1 of the scalar coherence field, where the potential VB(C) vanishes, the field energy density is negligible compared to radiation and matter, and all dynamical variables remain regular. The geometric singularity (a → 0, rho → infinity) persists as in standard GR; however, the Big Bang corresponds to the high-coherence limit C → 1, where the fundamental coherence field approaches its maximal value smoothly. The cosmological evolution corresponds to the monotonic decrease of C from ~1 toward Ctoday ~ 0.72, consistent with the range Ctoday in [0.70, 0.80] reported in Paper I, driven by Hubble friction and the potential gradient. Near C ~ 1 the field behaves as stiff matter (w → +1, rhoC proportional to a-6), a well-known scalar-field regime [6,13]. At the CMB epoch, rhoC/rhototal ~ 10-12, ensuring standard nucleosynthesis and recombination. No new parameters are introduced.