Maximizing-pattern conjecture for numerical ranges of cyclic shift matrices
Maximizing-pattern conjecture for numerical ranges of cyclic shift matrices
Let denote the cyclic shift matrix with weights . For , let and set
For a permutation , let be the cyclic shift matrix obtained by permuting the entries of , and let denote numerical range. Maximizing-pattern conjecture. For every ,
The stated pattern is known to maximize the numerical radius among permutations, and the conjecture asks whether it also maximizes the numerical range by set inclusion. The abstract reports this as established for and conjectures that the pattern extends to general ; the general case remains open.
Progress summary
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Sources & referencesView supporting material
Primary source
Mao-Ting Chien, Steve Kirkland, Chi-Kwong Li and Hiroshi Nakazato, “Numerical ranges of cyclic shift matrices”, arXiv:2304.06050 (2023).
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