@@ -373,7 +373,7 @@ A significant property of Hilbert spaces is that every closed subspace is comple
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\label{definition:hilbert-quadratic-function}
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\label{definition:hilbert-quadratic-function}
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Let $H$ be a complex Hilbert space and $q: H \to \complex$, then $q$ is \textbf{quadratic} if:
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Let $H$ be a complex Hilbert space and $q: H \to \complex$, then $q$ is \textbf{quadratic} if:
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\begin{enumerate}
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\begin{enumerate}
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\item For each $\lambda \in \complex$ and $\xi \in H$, $q(\lambda x) = |\lambda|^2 q(\xi)$.
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\item For each $\lambda \in \complex$ and $\xi \in H$, $q(\lambda \xi) = |\lambda|^2 q(\xi)$.
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\item (\textbf{Parallelogram Law}) For each $\xi, \eta \in H$,
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\item (\textbf{Parallelogram Law}) For each $\xi, \eta \in H$,
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\[
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\[
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q(\xi + \eta) + q(\xi - \eta) = 2q(\xi) + 2q(\eta)
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q(\xi + \eta) + q(\xi - \eta) = 2q(\xi) + 2q(\eta)
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@@ -70,7 +70,7 @@
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(T2) $\Rightarrow$ (T1): For each $n \in \natp$,
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(T2) $\Rightarrow$ (T1): For each $n \in \natp$,
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\begin{align*}
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\begin{align*}
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0 &\le \braks{\sum_{j = 1}^n E_{1j} \otimes z^j}^*\braks{\sum_{j = 1}^n E_{1j} \otimes z^j} = \sum_{j, k = 1}^n E_{jk} \otimes z^{j-k} \\
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0 &\le \braks{\sum_{j = 1}^n E_{j1} \otimes z^j}\braks{\sum_{j = 1}^n E_{j1} \otimes z^j}^* = \sum_{j, k = 1}^n E_{jk} \otimes z^{j-k} \\
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0 &\le \phi\braks{\sum_{j, k = 1}^n E_{jk} \otimes z^{j-k}} = \sum_{j, k = 1}^n E_{jk} \otimes A_{j - k}
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0 &\le \phi\braks{\sum_{j, k = 1}^n E_{jk} \otimes z^{j-k}} = \sum_{j, k = 1}^n E_{jk} \otimes A_{j - k}
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\end{align*}
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\end{align*}
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\end{proof}
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\end{proof}
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