The Vacuum Saturation Hypothesis: A Feasibility Analysis, Mathematical Formalization, and Testable Predictions

The Vacuum Saturation Hypothesis (VSH) proposes that the quantum vacuum possesses an intrinsic maximum energy density, implemented as a physical property of spacetime rather than a regularization artifact. Independent regions of space would independently settle to this maximum energy state regardless of whether they were ever in causal contact, thereby offering a candidate mechanism for the observed uniformity of the Cosmic Microwave Background (CMB) that does not invoke inflation, and simultaneously offering a candidate constraint on the vacuum energy density that bears on the cosmological constant problem. This document is organized in four parts. Part I presents a literature review establishing that no direct precedent for the combined VSH proposal exists in the peer-reviewed literature. Part II develops a preliminary mathematical formalization through a Born-Infeld-type nonlinear Lagrangian for the vacuum sector. Part III presents six falsifiable predictions including a predicted dark energy equation of state w(z=0) in the range −1 + 0.02 to −1 + 0.08, testable by Euclid DR1 (expected October 2026) and the DESI full survey (2027). Part IV presents a counterargument severity ranking, explicit self-audit flags, and a roadmap of required developments. This document does not contain complete derivations and should be understood as a conceptual framework and research proposal rather than a finished theoretical contribution. Expert feedback on an earlier version emphasized the importance of this distinction, and the framing has been revised accordingly. This document was prepared with Claude (Anthropic) as an AI-assisted research tool; all equations, derivations, and citations require independent verification by qualified theoretical physicists.