Completeness of unit shape for other Galois groups

Determine whether the unit shape uniquely determines number fields up to isomorphism in the other Galois-group families listed for unit-rank-2 number fields.

Background

The paper proves conditionally that the unit shape is a complete invariant for totally imaginary non-CM D6D_6-sextic fields, while showing that it is generally too weak an invariant for CM fields. The remaining Galois-group families may exhibit different behavior.

The authors leave unresolved whether the completeness result extends to other groups in the rank-2 classification. Resolving this would characterize the distinguishing power of unit shapes across the broader range of admissible families.

References

The possibility of extending the result of \Cref{theorem: Completeness of the shape} to other Galois groups listed in \Cref{prop:Galois groups rank 2}, in order to determine whether or not the unit shape determines the fields in the corresponding families uniquely, clearly warrants further investigation.

On the Geometry and Shapes of Rank 2 Log Unit Lattices  (2608.24736 - Cruz et al., 25 Aug 2026) in Section 7, Conclusion and future research