diff --git a/src/measure/measure/semifinite.tex b/src/measure/measure/semifinite.tex index 496987f..d08b5bb 100644 --- a/src/measure/measure/semifinite.tex +++ b/src/measure/measure/semifinite.tex @@ -59,3 +59,30 @@ \] \end{proof} + + +\begin{definition}[Scaffold*] +\label{definition:measure-scaffold} + Let $(X, \cm, \mu)$ be a measure space and $\cf \subset \bracs{A \in \cm|\mu(A) < \infty}$, then $\cf$ is a \textbf{scaffold} for $\mu$ if for all $E \in \cm$, + \[ + \mu(E) = \sup\bracs{\mu(E \cap A)|A \in \cf} + \] + + and the quadruple $(X, \cm, \cf, \mu)$ is a \textbf{scaffolded measure space}. +\end{definition} + +\begin{lemma} +\label{lemma:measure-scaffold-semifinite} + Let $(X, \cm, \mu)$ be a measure space: + \begin{enumerate} + \item If $\cf \subset \cm$ is a \hyperref[scaffold]{definition:measure-scaffold} for $\mu$, then $\mu$ is semifinite. + \item If $\mu$ is semifinite, then $\bracs{A \in \cm|\mu(A) < \infty}$ is a scaffold for $\mu$. + \end{enumerate} +\end{lemma} +% Omitted + +\begin{example} + Let $X$ be a LCH space, $\mu$ be a Radon measure, and $\mathcal{K}$ be the collection of compact subsets of $X$, then $\mathcal{K}$ is a scaffold for $\mu$. +\end{example} +% Omitted +