A structured numerical-range realization conjecture

About 5 years old · traced to

Let B∈Cd×dB\in \mathbb{C}^{d \times d}, and suppose that its numerical range W(B)\mathcal{W}(B) is invariant under multiplication by e2πi/ne^{2\pi i/n}. Let CC(n,d)\mathcal{C}_{\mathbb{C}}(n,d) denote the class of cyclic weighted shift matrices of size dd with cyclic structure parameter nn. Structured numerical-range realization conjecture. There exists A∈CC(n,d)A\in \mathcal{C}_{\mathbb{C}}(n,d) such that

W(A)=W(B).\mathcal{W}(A)=\mathcal{W}(B).

If W(B)\mathcal{W}(B) is also invariant under conjugation, the entries of AA can be chosen real. The preceding theorem establishes the analogous realization after enlarging the matrix size to n⌈d/n⌉n\lceil d/n\rceil; the conjecture asks whether the original size dd always suffices.

References

Primary source

Faye Pasley Simon and Cynthia Vinzant, “Invariant hyperbolic curves: determinantal representations and applications to the numerical range”, arXiv:2102.01726 (2021).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.