Vacuum Relaxation and the Effective Status of the Cosmological Constant in Late–Time Cosmology

Preprint. This manuscript is a preprint and has not been peer-reviewed. It is currently under consideration for publication in a peer-reviewed journal. The cosmological constant remains a central conceptual challenge in modern theoretical physics.While it provides an exceptionally successful effective description of the observed late–time acceleration of the Universe, its physical status and microscopic origin remain unresolved. In thiswork, we develop a methodological and interpretative analysis in which the cosmological constantis treated not as a fundamental constant of nature, but as an effective parameter characterizing thevacuum–metric state of the Universe. Within this perspective, cosmic acceleration is interpreted asa late–time manifestation of vacuum relaxation toward a quasi–stationary regime. The frameworkdoes not modify general relativity or quantum field theory, introduces no new dynamical degrees offreedom, and remains observationally degenerate with the standard ΛCDM model across currentlyaccessible regimes. Emphasis is placed on clarifying what the framework does and does not predict,on distinguishing interpretative reinterpretation from dynamical modification, and on formulatingmeaningful criteria for the possibility of refuting the hypothesis by observations. The analysis isexplicitly limited to conceptual, phenomenological, and consistency–based aspects of late–time cosmology and is intended to provide a coherent interpretative alternative to fundamental dark energyscenarios. KEY WORDS: Cosmological constant, vacuum–metric state, vacuum relaxation, cosmic acceleration, effective parameters, late-time cosmology, ΛCDM degeneracy, interpretative framework, observational refutability, phenomenological consistency