Phase-Dependent Vacuum Self-Screening: A Possible Framework for the Cosmological Constant Problem and Inflation

This research note explores a possible vacuum-response framework connecting the cosmological constant problem and early-universe inflation-like dynamics. The original motivation is the large discrepancy between the zero-point energy density expected from quantum field theory and the observed small effective cosmological constant. Instead of assuming an accidental cancellation of independent large contributions, the note considers the possibility that the local monopole component of zero-point stress is self-screened by a vacuum response associated with the stability of the vacuum phase. In the late-time stable phase, this self-screening suppresses the direct gravitational effect of local zero-point stress, while connected stress-tensor correlations may survive as a coarse-grained residue that behaves as an effective cosmological-constant-like component. The same framework is extended phenomenologically to the early universe by allowing the screening efficiency to depend on the vacuum phase. An early weakly screened phase may contain an unscreened vacuum-like stress component capable of driving inflation-like expansion, while relaxation toward the self-screened phase may provide a possible route toward reheating through the release of effective vacuum-sector energy. The note introduces effective stress tensors, local vacuum response, nonlinear response kernels, stress-correlation residues, and phase-dependent self-screening as elements of this framework. It does not claim a complete solution of the cosmological constant problem or a complete inflationary model. Instead, it presents a research program and identifies open problems, including the microscopic origin of the vacuum response, reheating dynamics, and primordial perturbation predictions.