What was already known
A dynamical-sampling survey conjectured this impossible for bounded normal operators. Nonexistence was known for self-adjoint operators, which cannot use the spectral rotations in this construction.
AI involvement
The authors say ChatGPT largely developed the construction. Krishtal and Pfander shaped the problem and explain the blockwise spectral rotation and frame estimates.
The original authors credit ChatGPT with largely developing the counterexample construction, while the human authors shaped and explained it.
Importance
The example resolves the named normal-operator question while preserving the narrower self-adjoint result.
Limitations
The paper provides a detailed proof, but no explicit completed check of its frame and Bessel estimates was documented.
Technical verification
The manuscript provides a proof but does not explicitly document a completed human review, proof-assistant check or exact certificate check of the construction.
Human understanding
The two human authors explain how blockwise rotating normal spectra concentrate the normalized orbit and yield a Riesz-basis subsequence plus a global Bessel bound.
Correction and publication history
The example resolves the named normal-operator question while preserving the narrower self-adjoint result.
Read this published revision