Sigma-algebras and measures
A sigma-algebra contains the whole space and is closed under complements and countable unions.
Key knowledge
A sigma-algebra contains the whole space and is closed under complements and countable unions. A measure assigns nonnegative extended values, gives the empty set zero and is countably additive on disjoint measurable sets; sigma-finiteness means a countable cover by finite-measure sets.
Conditions and scope
- A measure need not be defined on every subset.
- Borel sets are generated by the open sets of a topology.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Definitions 1.3, 1.8–1.9 and sigma-finite definition, sections 1.5–1.6.
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Entry details
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- math-measure-spaces
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- university-core.1
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- University core expansion