In this paper, we have obtained some conditions under which the boundary of the numerical range of tridiagonal matrices has no point spectrum. As a consequence of these results, the boundary of the numerical range of these tridiagonal matrices may be non-round only at the points where it touches the essential spectrum.

中文翻译：

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三对角矩阵数值范围边界上不存在点谱的准则

在本文中，我们获得了一些条件，在该条件下三对角矩阵的数值范围的边界没有点谱。这些结果的结果是，这些三对角矩阵的数值范围的边界可能仅在接触基本光谱的点处是非圆形的。