Wave-dominated systems admit rich superposed dynamics at the microscopic level, yet observed reality is dominated by a sparse set of effectively classical histories. Explaining this selection without invoking observer-dependent postulates remains a central problem across quantum foundations, semiclassical transport, and nonequilibrium physics. In this work, we establish a rigorous equivalence between two previously independent constraints on history viability: closure preservation in phase-space transport and coherence preservation under a context-induced metric. We prove that, within a physically relevant class of systems, transport-induced covariance growth and metric-induced distinguishability impose identical bounds on the admissible set of histories. This equivalence reveals history selection as a capacity-limited geometric process: histories persist if and only if their deformation remains within a finite coherence bandwidth. We further show that this bandwidth is not kinematic but must be maintained against transport load by sustained physical flux, giving rise to a natural thermodynamic structure without modifying underlying wave dynamics. Within this framework, entropy increase corresponds to loss of accessible distinction, the second law emerges as a no-free-bandwidth principle, and equilibrium appears as the zero-flux fixed point. Ontology itself is thereby reinterpreted as a thermodynamic phase: reality consists of those histories that remain dynamically viable under finite energetic support. The results provide a unified, observer-independent account of classicality, irreversibility, and history selection, with experimentally testable implications for coherence control and interference phenomena.
Wave-dominated systems admit rich superposed dynamics at the microscopic level, yet observed reality is dominated by a sparse set of effectively classical histories. Explaining this selection without invoking observer-dependent postulates remains a central problem across quantum foundations, semiclassical transport, and nonequilibrium physics. In this work, we establish a rigorous equivalence between two previously independent constraints on history viability: closure preservation in phase-space transport and coherence preservation under a context-induced metric. We prove that, within a physically relevant class of systems, transport-induced covariance growth and metric-induced distinguishability impose identical bounds on the admissible set of histories. This equivalence reveals history selection as a capacity-limited geometric process: histories persist if and only if their deformation remains within a finite coherence bandwidth. We further show that this bandwidth is not kinematic but must be maintained against transport load by sustained physical flux, giving rise to a natural thermodynamic structure without modifying underlying wave dynamics. Within this framework, entropy increase corresponds to loss of accessible distinction, the second law emerges as a no-free-bandwidth principle, and equilibrium appears as the zero-flux fixed point. Ontology itself is thereby reinterpreted as a thermodynamic phase: reality consists of those histories that remain dynamically viable under finite energetic support. The results provide a unified, observer-independent account of classicality, irreversibility, and history selection, with experimentally testable implications for coherence control and interference phenomena.
Decoherence and thermodynamic irreversibility are widely regarded as sufficient to explain the emergence of classical behavior from quantum mechanics. Decoherence suppresses interference between branches of the wavefunction, while entropy production provides a direction to macroscopic time. However, neither mechanism alone explains why macroscopic physics exhibits a single, persistent, globally consistent classical history rather than fragmentation into mutually incompatible record sets. In this work, we identify and formalize this unresolved issue as the classicality gap. We show that in finite systems subject to nonzero noise and irreversible record formation, decoherence and entropy production are generically insufficient to stabilize a single coherent macroscopic history. Instead, absent a history-level selection mechanism, redundant records diverge and macroscopic identity becomes ill-defined. We present a general instability result demonstrating this fragmentation tendency and introduce history-level constraint restoration as the minimal structural mechanism capable of preventing it. This mechanism operates without new microdynamics, collapse postulates, or observer dependence. We derive qualitative phase boundaries separating stable and unstable regimes and propose concrete experimental protocols on NISQ-era quantum platforms that can falsify the necessity of history selection. Our results establish that persistent classicality is not guaranteed by decoherence alone, but requires selection acting on histories under irreversible constraints. Keywords: classicality emergence, decoherence limits, record inconsistency, history instability, quantum-to-classical transition, irreversibility, entropy production, information persistence, open quantum systems, foundations of physics
The quantum measurement problem is commonly framed as a tension between unitary microscopic dynamics and the appearance of definite macroscopic outcomes. Decoherence theory explains the suppression of interference but does not explain why a single, persistent outcome is realized rather than a superposition of mutually incompatible macroscopic records. Interpretive responses—including collapse models, many-worlds branching, and observer-centric accounts—add ontological or epistemic structure beyond standard quantum mechanics. In this work, we show that such supplementation is unnecessary. We demonstrate that decoherence alone is generically insufficient to stabilize consistent macroscopic measurement histories under irreversible record formation. We introduce history-level coherence selection as a minimal structural requirement for persistent outcomes. This mechanism operates without modifying unitary dynamics, introducing collapse postulates, or invoking observers. We show that measurement outcomes correspond to stable, selection-supported histories rather than instantaneous state reductions. This reframing resolves the measurement problem by identifying the missing macroscopic mechanism—history selection under irreversible constraint—rather than by altering quantum theory. Keywords: quantum measurement problem, history selection, decoherence insufficiency, classical records, interpretation of quantum mechanics, consistent histories, irreversibility, information flow, foundational physics, measurement theory
The definition of entropy in both classical and quantum contexts relies on a coarse-graining of the underlying microscopic description. While this dependence is widely acknowledged, the physical constraints that determine which coarse-grainings are admissible are rarely made explicit. This issue becomes particularly acute when the universe is treated as a closed system, where no external observer or privileged level of description can be assumed. Any characterization of entropy — including claims about the low-entropy initial conditions of the universe — must then be grounded in descriptions that can be physically instantiated from within the system itself. In this work, we introduce a rigorous operational framework that establishes explicit physical selection principles over the space of admissible descriptions. We organize these criteria into necessary conditions (local accessibility and physical implementation via internal interactions) and practical sufficiency conditions (finite resource requirements anchored in Landauer’s principle, dynamical stability, and effective consistency). To demonstrate the validity of our framework, we introduce a concrete one-dimensional spin-chain toy model, illustrating how mathematically valid global partitions fail to be physically realizable due to dynamic propagation limits and informational constraints. We analyze the far-reaching implications of this restriction across three domains. In classical statistical mechanics, it limits the arbitrariness of macrostate definitions. In quantum theory, it identifies environment-induced decoherence (einselection) not merely as a formal tool, but as the objective dynamical mechanism that forces the emergence of admissible internal partitions. In cosmology, it resolves foundational circularities in the quasi-classical histories framework and reframes the thermodynamic arrow of time as a "doubly relational" property—dependent both on cosmic boundary conditions and on the material limits of internal subsystems. Our framework clarifies the operational status of entropy as an emergent property of physically instantiated descriptions within a universe that observes itself.
Quantum Darwinism explains the emergence of objective classical reality through redundant proliferation of information into the environment. While successful in symmetric, weakly noisy settings, the framework implicitly assumes that redundancy alone guarantees macroscopic stability. In this work, we demonstrate that redundancy and decoherence are insufficient to stabilize classical outcomes in the presence of irreversible record formation, asymmetric noise, or heterogeneous constraints. We introduce coherence selection as a distinct macroscopic mechanism operating at the level of histories rather than instantaneous states. Coherence selection acts as a structural filter on admissible histories, favoring those that maintain mutual consistency among redundant records under irreversible constraint. We show that Quantum Darwinism emerges as a special symmetric limit of this broader framework. Outside that limit, coherence selection is required to prevent fragmentation of macroscopic records. We identify regimes where coherence, rather than energy or entropy, dominates macroscopic outcomes, derive qualitative stability criteria, and propose falsifiable experimental tests. These results elevate coherence selection from a descriptive framework to a necessary macroscopic mechanism underlying persistent classicality.
This preprint is the third paper in a series on thermodynamic persistence and macroscopic identity. A recently proposed thermodynamic persistence constraint and its empirical test in biological and classical systems suggest that macroscopic identities operating under irreversible dynamics remain admissible only so long as cumulative irreversible dissipation remains finite. The condition does not introduce new dynamical laws or predict lifetimes; it excludes only those histories in which maintaining a coarse-grained identity would require unbounded irreversible entropy production. In this work I examine whether state-of-the-art superconducting qubit platforms are empirically compatible with such a persistence accounting. Using only published device parameters and order-of-magnitude estimates for control and dissipation, I construct an operational diagnostic quantity from independently measurable observables: coherence time, irreversible power dissipation, and device scale. I evaluate this diagnostic in two representative contexts: (i) idle coherence limited by energy relaxation and dephasing, and (ii) driven operation under repeated gate application as characterized by randomized benchmarking and error-per-gate metrics, including logical-level operation in surface-code experiments. Across these regimes, the empirical behavior mirrors that observed in classical and biological systems: coherence time and logical error rates vary primarily through changes in effective dissipation and noise, while the normalized cumulative irreversible burden associated with loss of a qubit’s operational identity remains finite and modest under realistic operating conditions. No violations of the proposed thermodynamic admissibility condition are found within the parameter ranges examined. These results do not establish a thermodynamic bound on quantum coherence or gate fidelities. They do, however, support the empirical viability of treating qubit-level persistence as constrained by cumulative irreversible effects within standard thermodynamic bookkeeping, in continuity with classical and biological 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.