The Validated Late-Time RCD Kernel is Strictly Parabolic: Principal Symbol Analysis and Absence of Causal Cone in Regime III

We analyze the linearized dynamics of the validated late-time coherence-field kernel of Radial Coherential Dynamics (RCD), the bistable Allen–Cahn / Wright–Fisher reaction–diffusion equation whose coarsening behavior in expanding Friedmann–Robertson–Walker (FRW) backgrounds was established in prior work [1]. Computing the principal symbol of the operator governing small perturbations δC about a homogeneous background, we find it strictly parabolic: the dispersion relation is purely imaginary in