Measure, Integration & Real Analysis · Problem 9B.8

Linear Maps on Hilbert Spaces — Sheldon Axler

Mathematics — Measure Theory · jordan-decomposition-positive-negative-parts

Problem

Suppose ν\nu is a real measure on a measurable space (X,S)(X, \mathcal{S}). Prove that ν+(E)=sup⁡{ν(D):D∈S and D⊆E}\nu^+(E) = \sup\{\nu(D) : D \in \mathcal{S} \text{ and } D \subseteq E\} and ν−(E)=−inf⁡{ν(D):D∈S and D⊆E}\nu^-(E) = -\inf\{\nu(D) : D \in \mathcal{S} \text{ and } D \subseteq E\} for all E∈SE \in \mathcal{S}.

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