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## 摘要

Let A and B be positive contractions on a Hilbert space. It was known before that the numerical range W(AB) of their product is contained in the rectangular region [−1/8,1]×[−1/4,1/4]. In this paper, we determine exactly when W(AB) touches on its four sides. This follows from the more general information on a containing region of W(AB) and on when they share a common tangent line. We also give an example of A and B on three-dimensional space for which W(AB) is not symmetric with respect to the x-axis.

原文 | ???core.languages.en_GB??? |
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頁（從 - 到） | 939-946 |

頁數 | 8 |

期刊 | Journal of Mathematical Analysis and Applications |

卷 | 455 |

發行號 | 2 |

DOIs | |

出版狀態 | 已出版 - 15 11月 2017 |

## 指紋

深入研究「Numerical ranges of products of two positive contractions」主題。共同形成了獨特的指紋。## 專案

- 1 已完成