GAC-Phase-Cosmology (GACPC) v4.2.5: An Effective Field Theory of Dissipative Scalar Interactions in a Layered Cosmological Medium and Addendum

We present GAC-Phase-Cosmology (GACPC) v4.2.5, a phenomenological Effective Field Theory (EFT) framework describing cosmological evolution as a dissipative interaction between multiple coupled scalar sectors. The model introduces a layered dynamical medium composed of three interacting fields (ϕ, χ, h) representing a primordial wavefront, a dissipative medium sector, and the Higgs-related structural sector. Primordial Resonance Damping (PRD) emerges naturally through effective energy transfer between fields, producing a dynamically evolving expansion history H(z) and a non-static dark sector equation of state w(z). The framework provides a unified interpretation of several current cosmological tensions, including the Hubble tension, suppressed structure growth (S8 tension), and early galaxy formation observed by JWST.