Structural Differentiation Cosmology (SDC) and Gravity (SDG): A Unified Structural Description of Cosmic Expansion and Gravitation

This work proposes Structural Differentiation Cosmology (SDC), a framework in which cosmic expansion is interpreted as a projection of irreversible internal structural differentiation within a closed universe. In contrast to the standard ΛCDM model, which relies on a cosmological constant and dark sector components, SDC introduces a structural density field C(t) that governs expansion through relational differentiation. At leading order, SDC reproduces ΛCDM-like expansion behavior, while predicting systematic and potentially observable deviations in ΔH/H. A key conceptual contribution of this work is the reinterpretation of the Big Bang. Rather than a true singular origin, the Big Bang is understood here as an effective description of a structurally saturated origin, removing the need for an initial spacetime singularity. The framework is further extended to gravity (SDG), where gravitational acceleration is described as emerging from gradients of structural density: g = -α ∇C(x,t) This provides a unified structural interpretation of both cosmology and gravity, linking expansion dynamics, structure formation, and gravitational phenomena within a single minimal framework. The model is falsifiable through observational signatures such as ΔH/H and offers a structural alternative to dark energy.