Jaime–Willett question on complexity rank of AT algebras

Is it true that every separable unital ATAT algebra AA of real rank zero satisfies cr⁡(A)≤1\operatorname{cr}(A)\le 1? In particular, for every irrational rotation algebra AθA_\theta with irrational θ\theta, is cr⁡(Aθ)=1\operatorname{cr}(A_\theta)=1?

References

Primary source

arXiv

Additional references

Progress summary

Refreshed
Claimed solved

A new unrefereed paper claims the question has a positive answer for every real-rank-zero AT algebra, but that claim has not been independently checked.

The 2023 paper Complexity rank for C∗C^*-algebras posed the question for irrational rotation algebras and, more generally, separable real-rank-zero ATAT-algebras that are not AFAF. It conjectured complexity rank one in these cases.

Known results

  • Every unital UCT Kirchberg algebra has complexity rank one or two; rank one occurs exactly when its K1K_1-group is torsion-free (2023).

New class-wide rank-one claim

The preprint Complexity Rank of AT Algebras of Real Rank Zero, by Qingnan An, Kang Li, and Zhichao Liu, claims a uniform rank-one bound for real-rank-zero ATAT-algebras and identifies irrational rotation algebras as rank one. The claim is unrefereed and has no independent mathematical verification in the retrieved sources.

Current status (as of October 2026): The rank-one conjecture for real-rank-zero ATAT-algebras is claimed to be settled by an unverified preprint; the earlier Kirchberg-algebra results remain established partial results.

Sources

Solutions 0

No solutions have been posted yet.