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@@ -23,7 +23,7 @@
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\]
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\]
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\end{lemma}
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\end{lemma}
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\begin{proof}[Proof, {{\cite[Lemma 15.6]{Zhu}}}. ]
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\begin{proof}[Proof, {{\cite[Lemma 15.6]{Zhu}}}. ]
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For each $y \in I$, $e_\beta y \to y$. Thus
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For each $y \in I$, $ye_\beta \to y$. Thus
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\[
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\[
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\limsup_{\beta \in B}\norm{xe_\beta - x}_A = \limsup_{\beta \in B}\norm{(x - y)(1 - e_\beta)}_A \le \norm{x - y}_A
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\limsup_{\beta \in B}\norm{xe_\beta - x}_A = \limsup_{\beta \in B}\norm{(x - y)(1 - e_\beta)}_A \le \norm{x - y}_A
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\]
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\]
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@@ -44,11 +44,11 @@
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For each $x \in A$ and $y \in I$,
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For each $x \in A$ and $y \in I$,
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\begin{align*}
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\begin{align*}
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\norm{x + I}_{A/I}^2 &= \lim_{\beta \in B}\norm{x - e_\beta x}_A^2 = \lim_{\beta \in B}\norm{(x - e_\beta x)(x - e_\beta x)^*}_A \\
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\norm{x + I}_{A/I}^2 &= \lim_{\beta \in B}\norm{x - xe_\beta }_A^2 = \lim_{\beta \in B}\norm{(x - xe_\beta )^*(x - x e_\beta)}_A \\
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&= \lim_{\beta \in B}\norm{(1_A - e_\beta)xx^*(1_A - e_\beta)}_A \\
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&= \lim_{\beta \in B}\norm{(1_A - e_\beta)x^*x(1_A - e_\beta)}_A \\
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&= \lim_{\beta \in B}\norm{(1_A - e_\beta)(xx^* + y)(1_A - e_\beta)}_A \le \norm{xx^* + y}_{A}
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&= \lim_{\beta \in B}\norm{(1_A - e_\beta)(x^*x + y)(1_A - e_\beta)}_A \le \norm{x^*x + y}_{A}
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\end{align*}
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\end{align*}
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As the above holds for all $y \in I$, $\norm{x + I}_{A/I}^2 \le \norm{xx^* + I}_{A}$. Thus $A/I$ equipped with the quotient norm is a $C^*$-algebra.
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As the above holds for all $y \in I$, $\norm{x + I}_{A/I}^2 \le \norm{x^*x + I}_{A/I}$. Thus $A/I$ equipped with the quotient norm is a $C^*$-algebra.
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\end{proof}
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\end{proof}
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