Abstract Sets of operators with numerical range contained in a given closed subset K of the complex plane are considered. A characterization of faces, and in particular extreme points, of these sets of operators is obtained when the underlying Hilbert space is finite dimensional and K is a closed polyhedron.

中文翻译：

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具有指定多面体中数值范围的一组算子的面

摘要 考虑包含在复平面的给定封闭子集 K 中的具有数值范围的算子集。当底层 Hilbert 空间是有限维且 K 是封闭多面体时，可以获得这些算子集的面的特征，尤其是极值点。