Approximating spin systems on planar graphs

Heng Guo, Xinyuan Zhang

For planar graphs at sufficiently small fixed hard-core activity, including λ≤1/1443, Guo and Zhang give a randomized polynomial-time approximation scheme for the partition function without a maximum-degree bound.

Sources for this record

What was already known

Earlier hard-core schemes required an activity bound that shrank with maximum degree. Planar graphs can have unbounded degree.

AI involvement AI-centered

Guo and Zhang credit GPT-5.6 Sol Ultra with the main proof ideas. They simplified, streamlined and wrote the proofs and explain the star-colouring and block-dynamics mechanism.

Guo and Zhang explicitly credit GPT-5.6 Sol Ultra with the main ideas of all proofs, while they simplified, streamlined and wrote the proofs.

Importance Notable

Gives an approximation scheme at constant activity across all planar graphs, improving the earlier degree-dependent scope.

Limitations

The paper also proves separate colouring hardness and two-spin results. Its written proof and author responsibility statement do not identify a completed check of this theorem.

Technical verification Reported

The source provides complete written proofs and an author responsibility statement, but no explicit completed proof check, formal check or reproducible test of the assessed theorem is documented. Reported is the evidence default.

Human understanding Full

The human authors supply a technical overview of the star-colouring/block-dynamics argument and say they simplified and wrote the proofs, explaining the central mechanism.

Correction and publication history

2026-10-18 · publication

Gives an approximation scheme at constant activity across all planar graphs, improving the earlier degree-dependent scope.

Read this published revision