Let $ mathcal P $ be the interior of a parabola of the complex plane. We show that, for all operators with numerical range contained in $ mathcal P $ , $ mathcal P $ is a 5-spectral set.
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机译：令数学式P $为复杂平面抛物线的内部。我们证明，对于$ mathcal P $中包含数值范围的所有算子，$ mathcal P $是5谱集。
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