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Sharp mass bounds for the two-dimensional O(4) model
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Abstract
We prove sharp mass bounds for the two-dimensional nearest-neighbor $O(4)$ model. For all sufficiently large inverse couplings β, the full transfer gap, including rotation-invariant local-observable sectors, is bounded above and below by positive multiples of $\sqrt\beta e^{-\pi\beta}$. We also prove that the model has a unique periodic local limit and a positive full gap at every finite β > 0, resolving the all-temperature lattice mass-generation conjecture for this periodic state. Under the stated cutoff scaling, the mass bounds are uniform in independently fixed physical units. A continuum spectral interpretation requires separate convergence hypotheses for the transfer semigroup and the block observables.
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Collected automatically by AI tools (Claude Opus 5.5 and GPT-6 Astra, 2026-10-23) and not checked by a person. May be wrong or incomplete. Report an error.
Follow-up works
- Anton Ragin, The massive continuum limit of the two-dimensional O(4) sigma model (Zenodo, doi:10.5281/zenodo.23349319, v7, 2026-10-13). Constructs an O(4) continuum limit "conditionally on results of two recent unrefereed, AI-generated manuscripts released by OpenAI", one being the renormalization-group analysis of the lattice O(4) model; this manuscript is in its citation list. [AI-generated per source]
Comments and discussion
- Peter Hall and Joseph Howlett, The most exciting claims from OpenAI's heap of new proofs (Scientific American, 2026-10-08). Reports several release papers claiming to resolve the sigma-model analogue of the Yang-Mills mass-gap problem, quoting Michael Douglas and Roland Bauerschmidt (the first sigma-model paper "seems very reasonable", the second "horrible") without identifying the papers by title. [family-level]
- kohatsootsich, comment in AI In Mathematics: October 10, 2026 (r/math, October 2026). Discusses the transfer-spectrum estimates in Lemma 2.1 and Proposition 2.2 as classical, responding to an AI-assisted comparison with the release’s Haldane-gap paper.
- Marcus Bintz (@spurious_bows), post on X (2026-10-11). Notes that the "squaring probabilities" trick of another release paper's Lemma 4.1 also appears as Lemma 2.1/Prop 2.2 here and as Lemma 8.2/Prop 8.3 in the O(3) continuum-limit paper.
- Marcus Bintz (@spurious_bows), post on X (2026-10-12). Lists this paper's Lemma 2.1 and Prop 2.2 as matching Lemma 4.1 and Prop 4.3 of the release paper The periodic spin-one Haldane gap [9/24].
Digests and expositions
- AI Proved What?, Do spins forget? (Episode 215, October 2026). Explains the five papers’ claims, proof strategies and differing formalization scopes. [AI-generated per source] [family-level]
Elsewhere
- Emergent Mind: family 215
Independent sites; their content is not reviewed here.
Cite
@misc{OAI:Sharp-mass-bounds-for-the-two-dimensional-O4-model-September-23-2026,
author = {{OpenAI}},
title = {{Sharp mass bounds for the two-dimensional O(4) model}},
howpublished = {OpenAI Math Release preprint
\href{https://github.com/openai/math/blob/main/preprints/Sharp-mass-bounds-for-the-two-dimensional-O4-model-September-23-2026/paper.pdf}{OAI:Sharp-mass-bounds-for-the-two-dimensional-O4-model-September-23-2026}},
year = {2026}
}Lean formalization
OpenAI provides Lean files for this family: lean/docs/215.md. The Lean statements have not been checked by people against the paper's claims.
Family 215: Canonical $O(3)$ continuum limit and exact $O(4)$ mass asymptotics
Constructs the canonical continuum limit of the two-dimensional nearest-neighbor $O(3)$ model: a non-Gaussian local relativistic theory with a unique vacuum and a positive mass gap. For the square-lattice $O(4)$ model, determines the exact leading asymptotic of the full transfer gap, $m_{\mathrm{lat}}(\beta)\sim32e^{\pi/4-1/2}\sqrt\beta\,e^{-\pi\beta}$. The family also proves exponential spin-correlation decay for two-dimensional nearest-neighbor $O(n)$ models with n ≥ 3 at every positive temperature.
Other papers in this family:
- The canonical massive continuum limit of the two-dimensional O(3) model · October 4, 2026
- An Isolated Particle Pole for the Two-Dimensional O(3) Spin Field · October 4, 2026
- Exact mass asymptotics for the two-dimensional O(4) lattice model · October 5, 2026
- Exponential decay in two-dimensional classical O(n) models · September 23, 2026