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author | Justin Gassner <justin.gassner@mailbox.org> | 2024-02-15 05:11:07 +0100 |
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committer | Justin Gassner <justin.gassner@mailbox.org> | 2024-02-15 05:11:07 +0100 |
commit | 7c66b227a494748e2a546fb85317accd00aebe53 (patch) | |
tree | 9c649667d2d024b90b32d36ca327ac4b2e7caeb2 /pages/functional-analysis-basics/the-fundamental-four/closed-graph-theorem.md | |
parent | 28407333ffceca9b99fae721c30e8ae146a863da (diff) | |
download | site-7c66b227a494748e2a546fb85317accd00aebe53.tar.zst |
Update
Diffstat (limited to 'pages/functional-analysis-basics/the-fundamental-four/closed-graph-theorem.md')
-rw-r--r-- | pages/functional-analysis-basics/the-fundamental-four/closed-graph-theorem.md | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/pages/functional-analysis-basics/the-fundamental-four/closed-graph-theorem.md b/pages/functional-analysis-basics/the-fundamental-four/closed-graph-theorem.md index f6a9783..e0ec62b 100644 --- a/pages/functional-analysis-basics/the-fundamental-four/closed-graph-theorem.md +++ b/pages/functional-analysis-basics/the-fundamental-four/closed-graph-theorem.md @@ -33,10 +33,11 @@ This shows that $\graph{T}$ is closed. Conversely, suppose that $\graph{T}$ is a closed subspace of $X \times Y$. Note that $X \times Y$ is a Banach space with norm $\norm{(x,y)} = \norm{x} + \norm{y}$. -Therefore $\graph{T}$ is itself as Banach space in the restricted norm $\norm{(x,Tx)} = \norm{x} + \norm{Tx}$. +Therefore, $\graph{T}$ is itself as Banach space in the restricted norm $\norm{(x,Tx)} = \norm{x} + \norm{Tx}$. The canonical projections $\pi_X : \graph{T} \to X$ and $\pi_Y : \graph{T} \to Y$ are bounded. -Clearly, $\pi_X$ is bijective, so its inverse $\pi_X^{-1} : X \to \graph{T}$ is a bounded operator by the +Clearly, $\pi_X$ is bijective, +so its inverse $\pi_X^{-1} : X \to \graph{T}$ is a bounded operator by the [Bounded Inverse Theorem](/pages/functional-analysis-basics/the-fundamental-four/open-mapping-theorem.html#bounded-inverse-theorem). -Consequently the composition, $\pi_Y \circ \pi_X^{-1} : X \to Y$ is bounded. +Consequently, the composition, $\pi_Y \circ \pi_X^{-1} : X \to Y$ is bounded. To complete the proof, observe that $\pi_Y \circ \pi_X^{-1} = T$. {% endproof %} |