The Universal Persistence Constraint: A Structural Accounting Principle for Identity in Open Systems

Physical theories describe how states change over time, yet all such descriptions implicitly presuppose that systems persist as identifiable entities long enough for change to be meaningful. In a universe governed by irreversible processes, this presupposition is nontrivial. Here we identify a universal structural constraint on persistence: any physical system that remains identifiable over time must satisfy a finite accounting bound on accumulated irreversible entropy production. The result introduces no new dynamics, forces, or mechanisms. Instead, it formalizes persistence as an admissibility condition on physical histories. We show that persistence is neither a state variable nor a dynamical law, but a structural requirement that precedes dynamical modeling. The constraint applies across domains— quantum, classical, biological, engineered, and cosmological—and provides a common account- ing language for identity, stability, and lifetime. The equality case marks the thermodynamic endpoint of admissible persistence, beyond which a system is no longer describable as the same entity.