Integral but non-superintegral polyhedral circle packings

Classify the integral polyhedral circle packings that are not superintegral.

Background

Polyhedral circle packings arise from the Koebe–Andreev–Thurston construction. A packing is integral when all circles have integer curvatures, while it is superintegral when the larger superpacking also has integer curvatures.

The paper’s arithmeticity classification gives a complete classification of superintegral polyhedra, because superintegrality implies arithmeticity. It does not resolve the broader class of integral packings that fail to be superintegral; the authors note that quasi-arithmeticity, rather than arithmeticity, is relevant in this setting.

References

On the level of polyhedral circle packings, it is an important open problem to classify the integral but not superintegral packings (see ).

Arithmetic Polyhedra  (2609.05349 - Allcock et al., 4 Sep 2026) in Section 6, Further Directions, item 6