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docs: 圆盘定理初步完成,添加部分习题 #72

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merged 3 commits into from
Sep 3, 2024

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shadowash0215
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@@ -843,6 +843,96 @@ \section{实数域与复数域的讨论}

\section{特征值的估计}

对于低阶的矩阵来说,我们可以通过解特征多项式来精确求得特征值;但对于高阶矩阵而言,解特征多项式是非常困难的,所幸相关的工作一般来说也不需要我们精确求得特征值,所以我们可以通过一些方法来估计特征值.

\begin{definition}{}{Gershgorin disks}
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定义定理名字还是用中文吧,或者至少中英对照

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这个是 label,定理的中文名字我也加一下吧

设 $T \in \mathcal{L}(V)$,并且 $v_1, \ldots, v_n$ 是 $V$ 的一组基,$D_i, i = 1, \ldots, n$ 是 $T$ 关于这组基的 Gershgorin 圆盘. 若 $\cup_{i = 1}^n D_i$ 是 $k$ 个不相交的连通区域 $R_1, \ldots, R_k$ 的并,并且 $R_r$ 是一个 $m_r$ 个 Gershgorin 圆盘的并,那么 $T$ 有 $m_r$ 个特征值落在 $R_r$ 中,$r = 1, \ldots, k$.
\end{theorem}

这一定理的证明需要用到特征值的连续性,这里不再赘述. 借助于这一条定理,我们限制了每个连通区域内特征值的个数,从而使得我们可以更好地估计特征值的位置. 而自然地,我们也可以利用 Gershgorin 圆盘来刻画一些与特征值有关的性质.
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不再赘述这个词有点怪

@yhwu-is yhwu-is merged commit 830da5b into yhwu-is:new Sep 3, 2024
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3 participants