Spacetime Porosity and the Spacetime Exclusion Principle: A Permeability-Based Field Theory of Gravity, Black Holes, Quantum Behavior, and Cosmology

We present a mathematically explicit effective field theory in which spacetime is not a universal geometric substrate but an emergent structure whose existence depends on local causal accessibility. Matter is characterized by a spacetime permeability field κ ∈ [0, 1], with ordinary atomic matter being spacetime porous and black hole interiors corresponding to complete spacetime exclusion. We introduce the Spacetime Exclusion Principle, stating that spacetime degrees of freedom are absent wherever κ = 0. Gravity arises from resistance to spacetime flow rather than intrinsic curvature of matter. A variational principle governing spacetime flow and permeability is formulated, from which the field equations are derived. Newtonian gravity, Schwarzschild and Kerr exterior geometries, gravitational waves, and standard cosmology emerge as effective limits. Black hole interiors are shown to be ontologically and mathematically disconnected from the exterior, with all physical observables encoded as boundary data at causal saturation surfaces. Singularities are eliminated by construction. Quantum mechanical behavior is interpreted as a consequence of fragmented spacetime accessibility at microscopic scales.