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Question

Math 6210 • Real Analysis

Fall 2022 • Question 1

Let \((X, \mathcal {M}, \mu )\) be a measure space and \(f : X \to Y\) be a function.

  1. Show that \(\mathcal {N} = \{f^{-1}A : A \in \mathcal {M}\}\) is a \(\sigma \)-algebra.
  2. Let \(\nu (B) = \mu (f(B))\) for \(B \in \mathcal {N}\). Show that \(\nu \) is a measure.
  3. Show that even if \((X, \mathcal {M}, \mu )\) is complete we do not necessarily have that \((Y, \mathcal {N}, \nu )\) is complete.

Raw LaTeX

Let \((X, \mathcal{M}, \mu)\) be a measure space and \(f : X \to Y\) be a function.
\begin{enumerate}

\item
Show that \(\mathcal{N} = \{f^{-1}A : A \in \mathcal{M}\}\) is a \(\sigma\)-algebra.


\item
Let \(\nu(B) = \mu(f(B))\) for \(B \in \mathcal{N}\). Show that \(\nu\) is a measure.


\item
Show that even if \((X, \mathcal{M}, \mu)\) is complete we do not necessarily have
that \((Y, \mathcal{N}, \nu)\) is complete.

\end{enumerate}