Variation of Signed Measure is Measure
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Theorem
Let $\struct {X, \Sigma}$ be a measurable space.
Let $\mu$ be a signed measure on $\struct {X, \Sigma}$.
Let $\size \mu$ be the variation of $\mu$.
Then $\size \mu$ is a measure.
Proof
Let $\tuple {\mu^+, \mu^-}$ be the Jordan decomposition of $\mu$.
Then:
- $\size \mu = \mu^+ + \mu^-$
So $\size \mu$ is a measure from Linear Combination of Measures.
$\blacksquare$