Physical Constraints on the Interpretation of Time in Multipartite Quantum States

This manuscript provides a physical consistency analysis of the spacetime quantum state framework introduced by Lie and Fullwood. It does not propose a new quantum theory, alter quantum mechanics, or introduce new formal structures. Instead, it identifies a necessary physical constraint on how the temporal parameter appearing in multipartite quantum states must be interpreted when the framework is applied to relativistic observers or extended-duration processes. The analysis shows that treating time as a purely linear or informational parameter admits unphysical divergences, including requirements for unbounded energetic or informational resources. To resolve this, the paper applies Stabilized Proper Time (SPT)—a previously developed bounded regulator—to enforce relativistic and energetic consistency while preserving the original spacetime-state formalism, including linearity and quantum conditionability. The result is a regulator-based interpretive clarification that yields falsifiable predictions without modifying the underlying theory. This work should be read as a constraint and admissibility condition on the physical use of spacetime quantum states, rather than as a competing or replacement framework.