Lebesgue integral and integrability
Integration starts from measurable simple functions.
Key knowledge
On a measure space, the integral of a nonnegative measurable f is the supremum of integrals of nonnegative simple functions below f. A real measurable f is integrable when ∫|f|dμ<∞; then ∫f=∫f⁺−∫f⁻.
Conditions and scope
- Specify the measure and measurable domain.
- An expression ∞−∞ does not define a signed integral.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Sections 4.1–4.2; Definition 4.8: supremum over simple functions and integrability via absolute integral.
2026-10-10 · Nonnegative construction and finite signed integrability.
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