Boundary-Conditioned Thermodynamics: Non-Isothermal Fixed Points, Effective Accessibility, and Work Extraction from Kernel-Conditioned Structural Bias

This record presents a foundational manuscript proposing boundary-conditioned thermodynamics, a framework in which thermal equilibrium is treated not only as a static entropy maximum, but as a fixed point selected by physical exchange structures. In conventional thermodynamics, a thermal reservoir is often idealized as a featureless body characterized by a scalar temperature. The present work argues that this description can be incomplete when boundary processes themselves filter and reshape the accessible microscopic states. Gas--wall exchange, adsorption potentials, phonon-mediated re-emission, and boundary transition kernels can define a stationary state through a cycle condition, f^=Lf^. In this view, equilibrium is not only a state; it is also a fixed point of an exchange structure. The manuscript develops this idea through the Izumi-type mechanism, focusing on Bose--Einstein-type boundary kernels with unequal adsorption potentials. It introduces effective accessibility, effective entropy, kernel compatibility, structural non-isothermal fixed points, and the possibility of work extraction from kernel-conditioned structural bias. The work preserves microscopic energy conservation while examining whether the conventional scalar-temperature reservoir model is sufficient for all boundary-conditioned systems. The purpose of this record is to provide a theoretical foundation and reference document for future discussion, simulation, and experimental testing. The immediate experimental priority is not engine construction, but verification or falsification of the predicted structural non-isothermal fixed point and its dependence on adsorption asymmetry. This work is intended as a starting point for a broader research direction in which thermodynamics is extended from the study of material states to the study of exchange structures, boundary kernels, and the fixed points they select.