Added section regarding the duality of L^p spaces.

This commit is contained in:
Bokuan Li
2026-06-15 21:47:49 -04:00
parent 35efec2d90
commit dadddc4663
6 changed files with 240 additions and 7 deletions

View File

@@ -23,11 +23,13 @@
\begin{definition}[Hölder conjugates]
\label{definition:holder-conjugates}
Let $p, q \in (1, \infty)$, then $p$ and $q$ are \textbf{Hölder conjugates} if
Let $p, q \in [1, \infty]$, then $p$ and $q$ are \textbf{Hölder conjugates} if
\[
\frac{1}{p} + \frac{1}{q} = 1
\]
under the identification that $1/\infty = 0$.
\end{definition}
\begin{lemma}
@@ -40,15 +42,15 @@
\end{lemma}
\begin{theorem}[Hölder's Inequality, {{\cite[6.2]{Folland}}}]
\begin{theorem}[Hölder's Inequality]
\label{theorem:holder}
Let $(X, \cm, \mu)$ be a measure space, $E, F$ be a normed vector spaces, $p, q \in [1, \infty]$. If $p, q$ are Hölder conjugates or if $p = 1$ and $q = \infty$, then for any $f \in \mathcal{L}^p(X; E)$ and $g \in \mathcal{L}^q(X; F)$,
Let $(X, \cm, \mu)$ be a measure space, $E, F$ be a normed vector spaces, $p, q \in [1, \infty]$ be Hölder conjugates, then for any $f \in \mathcal{L}^p(X; E)$ and $g \in \mathcal{L}^q(X; F)$,
\[
\int \norm{f}_E \norm{g}_F d\mu \le \norm{f}_{L^p(X; E)}\norm{g}_{L^q(X; F)}
\]
\end{theorem}
\begin{proof}
\begin{proof}[Proof, {{\cite[Theorem 6.2]{Folland}}}. ]
First suppose that $p = 1$ and $q = \infty$. In this case,
\[
\int \norm{f}_E \norm{g}_F d\mu \le \norm{g}_{L^\infty(X; F)}\int \norm{f}_Ed\mu = \norm{f}_{L^1(X; E)}\norm{g}_{L^\infty(X; F)}