Admissible Quantum Histories Under Irreversibility A Thermodynamic Constraint on Open Quantum Systems

This preprint develops a thermodynamic admissibility condition on the persistence of quantum identity in open systems. Standard quantum mechanics allows extremely large spaces of possible system histories, but only a small subset remains experimentally realisable once irreversible entropy production is taken into account. This work formalizes this as an admissibility constraint: any quantum system that preserves a stable, trackable identity over time must satisfy a finite budget on cumulative irreversible dissipation. No new forces, variables, or dynamics are added; the constraint is purely structural and compatible with existing open-systems formalisms. The paper connects this requirement with decoherence, spectrum broadcasting, quantum Darwinism, and the emergence of classical objectivity. It frames identity persistence as a pre-dynamical condition—necessary before predictions about evolution or measurement outcomes are meaningful. This structural account clarifies why only certain histories are physically realisable, how objectivity arises under irreversibility, and how thermodynamic bookkeeping parameters (such as an “identity budget”) implicitly constrain experimental practice. The result provides a unifying, thermodynamically grounded framework linking dissipative quantum processes, system architecture, and long-term identifiability.