Unified Spacetime Dynamics in the R5+ Framework: Strong Gravity, Thermodynamic Regularization, and Field-Theoretic Entropy Production

This paper extends R5+to the strong-gravity regime (Kretschmann-anchored Proca hair, regularized blackhole thermodynamics) and demonstrates that the effective viscosity arising from the Symmetron-Proca coupling generates a new field-theoretic source of entropy production, with a sharp peak at the Symmetron phase transition z∗= 0.65. This provides a dynamical mechanism reinforcing the thermodynamic arrow of time at late cosmic epochs, distinct from primordial entropy generated during the Big Bang and structure formation. Five falsifiable predictions are formulated for LISA, ngEHT, and large-scale structure surveys. A rigorous field-theoretic derivation of the anomalous dimension identification is deferred to future work. Keywords Modified Gravity, General Relativity Extension, Symmetron Field, Proca Field, Fluid Geometry, Galactic Dynamics, Astrophysics, Theoretical Physics, Open Science