Mathematics_for_Physicists/chapters/sections/stieltjes.tex
2021-04-01 00:38:45 +02:00

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\documentclass[../../script.tex]{subfiles}
\begin{document}
\section{Lebesgue-Stieltjes Integral}
\begin{defi}
Let $F: \realn \rightarrow \realn$ be a monotonically increasing, continuous function. Then we set
\begin{align*}
\lambda_F(\varnothing) := 0 && \lambda_F((a, b]) = F(b) - F(a), ~~(a, b] \in \intervals
\end{align*}
\end{defi}
\begin{thm}
$\lambda_F$ is a measure on $H$.
\end{thm}
\begin{proof}
Without proof.
\end{proof}
\begin{defi}
The integral
\[
\int_A f \dd{\lambda_F}
\]
is called the Lebesgue-Stieltjes integral on $\realn$ and is denoted by
\[
\int_A f(x) \dd{F(x)} := \int_A f \dd{\lambda_F}
\]
If $A = [a, b]$, then we write
\[
\int_a^b f(x) \dd{F(x)}
\]
\end{defi}
\end{document}