The Refractive Vacuum Hypothesis: A Non-Markovian EFT Upgrade of Informational Viscosity in a 5D Bulk Framework

This preprint develops a non-Markovian upgrade of the MetaTime refractive-vacuum framework by reformulating the vacuum as an effective structured medium with causal memory, finite relaxation time, and protocol-dependent response. Instead of assuming an instantaneous constitutive relation, the manuscript introduces a latent state variable governed by a memory kernel and a minimal relaxation equation, allowing the effective refractive response of the vacuum to depend on prior excitation history. Within this effective-field-theory perspective, the observed propagation speed is treated as an emergent constitutive quantity rather than as a primitive kinematic input.The paper formulates three main phenomenological signatures: hysteresis under cyclic driving, memory-dependent lag in propagation, and exponential relaxation (“healing”) of the effective vacuum response after strong excitation. It further imposes complete positivity, trace preservation, and operational no-signaling on the observable brane dynamics, thereby separating the effective structured-medium description from stronger ontological claims about higher-dimensional bulk completion. The 5D MetaTime architecture is retained as a geometric embedding, but the manuscript is written so that the non-Markovian vacuum EFT stands on its own as a falsifiable framework.This work is presented as a theoretical preprint in information-inspired field theory and open-system phenomenology. It does not claim that recent optical or condensed-matter experiments directly confirm the 5D interpretation; rather, it argues that a non-Markovian constitutive vacuum description provides a more rigorous and testable effective layer for the broader MetaTime program.