Observation

Phase transition refuses to be classified as symbolic. Every other thermodynamic concept in this session — entropy, enthalpy, Gibbs free energy, the second law, thermal equilibrium, heat transfer — carries the Symbolic trait, marking them as representations of something beyond themselves. Phase transition alone receives State-Transforming plus Temporal, landing at 00100200 with Jaccard as low as 0.0 against jurisprudence and 0.077 against game theory. Within its own domain, its nearest neighbour sits at Jaccard 0.20. UHT sees it not as a description of reality but as something that does something — a process, not a principle.

The second surprise: enthalpy and Gibbs free energy are classified identically at 0000A000, and that hex code is shared exactly with information theory’s channel capacity. Three quantities from two unrelated domains, indistinguishable in UHT space.

Evidence

Seven thermodynamic entities classified: entropy (0004A200), second law (0000A200), enthalpy (0000A000), thermal equilibrium (0000A200), Gibbs free energy (0000A000), heat transfer (00002200), phase transition (00100200). Intra-domain Jaccard from entropy: 0.75 to second law and thermal equilibrium, 0.50 to enthalpy/Gibbs/heat transfer, 0.20 to phase transition. Cross-domain: thermodynamic entropy to information-theoretic channel capacity 0.50, to mutual information 0.40, to KL divergence 0.20. Thermal equilibrium to control theory’s system stability 0.20, to reliability’s fault tolerance 0.20, to risk mitigation 0.429. Phase transition to mechanism design 0.077, to key exchange 0.062, to judicial review 0.0.

Interpretation

UHT draws a hard line between quantities-as-descriptions and processes-as-transformations. Phase transition is the only thermodynamic concept that crosses that line. This aligns with the earlier finding (HYP-004, confirmed) that UHT clusters by semantic role rather than domain vocabulary — phase transition’s role is genuinely different from entropy’s, regardless of their shared domain. The enthalpy/channel capacity convergence reinforces this: both are “amount-of-something” measures governed by formal rules, and UHT treats them as structurally identical. The low Jaccard between thermal equilibrium and system stability (0.20) is harder to explain — equilibrium and stability share deep conceptual structure, but UHT apparently distinguishes their trait profiles enough to separate them.

Action

Recorded as COR-DOMAINEXPANSIONS-012. Baseline BL-UHTRESEARCH-022 created. The phase transition outlier and the enthalpy/channel capacity convergence both suggest a calibration hypothesis worth testing: whether all “state-change process” concepts across domains cluster together in UHT space the way “formal quantity” concepts do. Next session should consider formulating this as a testable hypothesis if CALIBRATION is selected.