Free Fermions in Disguise without Exponential Degeneracies
An existence question settled by exhibiting an object, not a general theorem: one model in the family has no exponential degeneracies for generic couplings, and nothing here says which others do. The route is worth recording because it is not the one anyone was looking down. The author had tried and failed to find such a model directly. It surfaced instead from an unrelated classification of medium-range spin chains, where the AI's computations produced a list of integrable Hamiltonians and one of them combined two terms of a standard XY chain with two of Fendley's FFD model, a combination nobody had considered. The author noticed it in the list; the rest followed from asking the model a sequence of increasingly specific questions.
Exact FrontierDelta
Scope and record
Occurred: Oct 29, 2026
Delta type: REGISTRY REVISION
Assumptions: VibeMathed verification: unreviewed. Publication: preprint. AI contribution: ai-co-developed. VibeMathed editorial classifications, scores, notes, relations, and dataset structure are CC BY 4.0. Source statements and linked content retain their own rights.
Canonical aliases: Free Fermions in Disguise without Exponential Degeneracies · FFD without exponential degeneracies
Confidence: Not scored
Registry verification: unreviewed · preprint · resolved
Attribution
VibeMathed
registry · event recorded by
ChatGPT 5.4 Pro
model · ai model contributor · OpenAI
ChatGPT 5.5 Pro
model · ai model contributor · OpenAI
Balázs Pozsgay
human · human collaborator
Lineage and corrections
Corrects Free Fermions in Disguise without Exponential Degeneracies →
Supersedes Free Fermions in Disguise without Exponential Degeneracies →
This event attributed to ChatGPT 5.4 Pro
Free Fermions in Disguise without Exponential Degeneracies evidence for this event
An existence question settled by exhibiting an object, not a general theorem: one model in the family has no exponential degeneracies for generic couplings, and nothing here says which others do. The route is worth recording because it is not the one anyone was looking down. The author had tried and failed to find such a model directly. It surfaced instead from an unrelated classification of medium-range spin chains, where the AI's computations produced a list of integrable Hamiltonians and one of them combined two terms of a standard XY chain with two of Fendley's FFD model, a combination nobody had considered. The author noticed it in the list; the rest followed from asking the model a sequence of increasingly specific questions. parent of this event
Supplemental Material: the author's itemised account of what the AI contributed evidence for this event
Fendley and Pozsgay, Free fermions beyond Jordan and Wigner (SciPost 2024) evidence for this event
This event attributed to Balázs Pozsgay
Free Fermions in Disguise without Exponential Degeneracies parent of this event
Elman, Chapman and Flammia, Free fermions behind the disguise (CMP 2021) evidence for this event
VibeMathed record: Free Fermions in Disguise without Exponential Degeneracies evidence for this event
This event attributed to ChatGPT 5.5 Pro
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