Open Universe Model: Unitarity as a Local Approximation (Supplement to Article 8 – A Hypothetical Extension)

This article proposes an open universe model as a supplement to Article 8 of the main series. Global unitarity (reversibility of quantum evolution) is not required for our Universe as a whole. Instead, unitarity is preserved for a larger closed system that includes our Universe and external objects – half‑spaces A and B from the interference vacuum model, as well as neighbouring universes. Our Universe is treated as an open quantum subsystem whose evolution may be non‑unitary, with deviations from unitarity explained by the exchange of correlations with the external environment. The model does not solve the problem of quantum gravity, but circumvents it by changing the formulation of the question. It allows relaxing the requirement of global unitarity without undermining the scientific method: local predictability is preserved, while global uncertainty is shifted to observationally inaccessible regions. It is shown how the open universe model circumvents or reformulates the nine problems listed in Article 8: the absence of a full quantum theory of gravity, the absence of a rigorous theory for the expanding Universe (dS), the experimental unverifiability of collapsar radiation, the complementarity problem, the absence of dS/CFT, the need to account for backreaction, the lack of a unified framework for 4D collapsars, the controversial “transparency of the horizon”, and the absence of a dynamical mechanism for recovering the initial state. Recovery of the state is not required, since “information” in the ontic sense is not regarded as a physical entity that must be preserved. The model builds on contemporary research on open quantum systems in cosmology (Open EFT, MIU) and is ontologically connected to the interference vacuum. Keywords: open universe, unitarity, decoherence, quantum open systems, dS/CFT, MIU, interference vacuum.