Thermalization Without Equilibrium

Arc II — Observation Paper 1 Title Thermalization Without Equilibrium Zenodo DOI 10.5281/zenodo.18180820 Description This paper demonstrates that thermal behavior does not require equilibrium ensembles, microscopic ergodicity, or underlying statistical assumptions. Instead, thermalization is shown to arise from the progressive degradation of accessible correlations under finite observational capacity. The analysis reframes temperature, entropy production, and apparent equilibration as operational phenomena: when observers lose the ability to resolve fine-grained correlations, remaining observables converge toward thermal statistics regardless of the underlying dynamics. Thermal distributions therefore emerge as inference-fixed points under accessibility constraints, not as properties of microscopic phase space. By constructing thermalization without reference to microstates or equilibration timescales, the paper resolves long-standing conceptual tensions between thermodynamics and unitary dynamics. It clarifies why thermal behavior appears robust across systems with vastly different microscopic laws. This framework applies equally to classical, quantum, and gravitational settings, including horizon-induced thermality and detector responses in curved spacetime. Thermal behavior is shown to be a consequence of observational saturation rather than dynamical relaxation. Keywords thermalization; entropy production; irreversibility; operational thermodynamics; accessibility limits; non-equilibrium physics Notes Arc II — Observation (foundational) Thermal behavior derived without equilibrium assumptions Temperature as an inference artifact Applies to classical, quantum, and gravitational systems Conceptual bridge between entropy (Arc I) and measurement