Causal Decoupling Isolation in Closed FLRW Cosmology

This preprint presents Version 1.0 of the Causal Decoupling Isolation (CDI) framework, a theoretical investigation of permanent macroscopic classical causal disconnection within closed Friedmann–Lemaître–Robertson–Walker (FLRW) cosmology. The work develops a geometry-first relativistic framework based on General Relativity, Lorentzian causal structure, null geodesics, cosmological event horizons, and globally hyperbolic spacetime. It rigorously distinguishes spatial topology from causal accessibility and demonstrates that permanent classical causal isolation arises from finite future conformal reach rather than spatial closure alone. Within the closed FLRW model, the framework establishes that sufficiently separated comoving domains become permanently classically causally disconnected when the comoving separation exceeds the future event-horizon reach under accelerated cosmological expansion. The resulting causal condition is formulated using null-geodesic propagation and conformal geometry while remaining fully consistent with Einstein's field equations and relativistic causal structure. The framework further distinguishes macroscopic classical causal isolation from quantum correlations. It is fully compatible with the relativistic no-signaling theorem, allowing pre-existing quantum entanglement to persist while excluding any controllable superluminal transfer of classical information. This work does not propose a multiverse theory, closed timelike curves, wormhole communication, or modifications of General Relativity. Instead, it provides a mathematically disciplined formalization of permanent classical causal isolation within the standard framework of relativistic cosmology. Version 1.0 establishes the foundational formulation of the CDI framework. Future editions may further extend its mathematical derivations, numerical cosmological analyses, observational comparisons, and broader applications while preserving the central theoretical principles established in this work. Keywords: General Relativity, FLRW Cosmology, Lorentzian Geometry, Causal Structure, Cosmological Event Horizon, Classical Causal Isolation, Null Geodesics, Global Hyperbolicity, Closed Cosmology.