Continuity Closure and Inflationary Cosmology

Inflationary cosmology is usually built in layers. One begins with a background spacetime, introduces a scalar field, defines perturbations, and then quantises those perturbations to obtain observable structure. The construction works, but it proceeds by successive assumptions. This work takes a different route. It begins from a single covariant statement: that a temporal density is conserved under flow. With minimal stress closure imposed, the system is allowed to evolve without introducing a scalar field, potential, or perturbative sector as primitive inputs. From this starting point, the standard structure of inflation is recovered rather than assumed. Homogeneous expansion arises as the symmetric limit of conserved redistribution. Accelerated expansion appears as a branch of the closure relation when effective pressure approaches the negative of the density. Perturbations follow as variations of the conserved current and reduce, after constraint resolution, to the familiar Mukhanov–Sasaki form. The scalar and tensor spectra emerge with their standard structure, evaluated at horizon crossing of the flow. The scalar field description is not removed but repositioned. It appears as a coordinate representation of a restricted class of irrotational flows. In this sense, the inflaton is not a primitive ingredient but a parametrisation of the underlying conserved system. A complete structural correspondence with the standard inflationary framework is provided. Background dynamics, slow-roll behaviour, perturbations, quantisation, reheating, and observational mapping are all recovered within the same continuity-closed formulation. No new numerical predictions are claimed at minimal closure level. Instead, the framework fixes the invariant structure of the theory while identifying the remaining elements as explicit closure targets, including amplitude, nonlinear statistics, reheating couplings, and the microscopic origin of the closure relation. The purpose is not to replace the standard construction, but to reorganise it. The inflationary pipeline is shown to follow from a more constrained starting point, with independent assumptions reduced and their roles made explicit.