Astra-origin construction gives discontinuous traces

Sauers constructs a separable unital C*-algebra with compact nonempty trace space whose uniform tracial completion has a trace discontinuous in the uniform 2-norm, and a factorial tracially complete pair with the same failure.

Sources for this record

What was already known

Carrion and coauthors asked the factorial-pair question, and Schafhauser, Tikuisis and White posed the completion form as Problem XXII. Related homogeneous-block and commutator obstructions were known.

AI involvement AI-led

Sauers directed the project; the repository credits Astra with the counterexample argument, Claude with exposition and Lean work, and Codex with Lean and submission work.

Astra is explicitly credited with developing the original retained counterexample argument; Sauers directed the project.

Importance Notable

The unconditional constructions answer two stated questions about traces on tracial completions.

Limitations

Neither construction is claimed to be nuclear or simple. The source’s historical priority search is limited, and no human expert proof review is documented.

Technical verification Formal (Lean 4 kernel, Comparator and NanoDa)

The repository reports a full Lean build, definition-model and axiom checks, exact Comparator statement comparison and Lean/NanoDa replay. The successful run is tied to an earlier source revision with a documented byte-equivalent Lean package at the cited revision; this review did not independently replay it.

Formal checking

Full build, definition checks, statement comparison, axiom audit and independent proof replay; final-package workflow checks Lean-byte equivalence to verified revision

Checker
Lean, Comparator and NanoDa in the reported GitHub Actions run
Scope
Both unconditional discontinuous-trace existence theorems selected for Palomar
Basis
Reported by the linked checker
Evidence source

Checking a formal statement does not establish that it matches the original problem.

Human understanding Few

No named human explanation of the central antipodal-block/corona-trace proof is documented. The detailed proof account is credited to Codex, and the source reports no human expert review; Few is the evidence-gap default.

Correction and publication history

2026-10-18 · publication

The unconditional constructions answer two stated questions about traces on tracial completions.

Read this published revision