A Closure-Complete Primordial Alternative to Inflation from Complete Detectable Spacetime Geometry

Inflationary cosmology successfully explains the observed large-scale coherence of the universe, the near-scale-invariant primordial spectrum, and the acoustic structure of the cosmic microwave background. Yet the primordial mechanism underlying inflation remains conceptually incomplete: the inflation field has not been independently observed, the inflation potential remains fundamentally unconstrained, and the framework inherits persistent difficulties involving false-vacuum metastability, trans-Planckian sensitivity, eternal inflation, and measure ambiguities. In the present work, Complete Detectable Spacetime Geometry (CDSG) provides a closure-complete non-inflationary primordial alternative, in which primordial structure emerges not from fluctuations of a scalar inflation field on a pre-existing spacetime background, but from covariance fluctuations of admissible recirculating spacetime action histories. Within this framework, the closure phase and closure field define the primitive spacetime-action covariance structure, while effective geometry emerges only after coarse-graining closure covariance. The resulting primordial mechanism proposes leading-order explanations for several principal observed primordial signatures without introducing an inflation sector, scalar potential, false-vacuum decay, or exponential de Sitter expansion. The framework also suggests a natural interpretation of JWST-era early-structure observations, including compact high-redshift sources and rapidly assembled massive galaxies, as possible signatures of efficient early closure-covariance organization. Conceptually, the framework replaces the standard inflationary ordering (background metric → inflation fluctuations → primordial structure). with the CDSG ordering (closure ensemble → g_eff_μν → primordial structure). This removes the need for a primitive inflation field or inflationary potential, preserves relativistic causality without requiring inflationary horizon stretching, reformulates the classical Big Bang singularity as a feature of the coarse-grained emergent metric description rather than a primitive ontological boundary, and suggests a new ultraviolet organization of primordial cosmology through compact closure structure. Preliminary transfer-level calculations indicate compatibility with the observed TT, TE, and EE acoustic hierarchy using closure-derived primordial parameters. The resulting theory provides a falsifiable non-inflationary primordial cosmological program grounded in closure-complete spacetime covariance.