DefinitionDefinition: Literature-sourcedProof: Not applicablejudge pass (deepseek-v4-pro + gpt-5.6-terra)audited 2026-08-21
How statement and proof provenance work
The first chip identifies the source of the statement or construction; the second identifies the source of its local proof or verification.
- Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
- AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
- AI-generated: a genuinely novel statement formulated by AI, with no source for the claim itself.
These labels describe origin, not correctness: citations and verification chips remain separate evidence.
Finite, sigma-finite, and semifinite measures
Definition
Let be a measure space (Measure spaces).
- The measure is finite if .
- It is sigma-finite if there is a sequence in such that and for every .
- It is semifinite if, whenever and , there is with and .
The last condition is automatic when , by taking ; its substantive case is .
Depends on
Used by
- Dominated convergence is a Vitali corollary Corollary
- Measurable Hilbert field from a countable fundamental family Definition
- The semifinite part of a measure Definition
- A Hilbert–Schmidt kernel operator is compact on L two Example
- A square-integrable separable product kernel Example
- Adjoints of shifts, multiplication and integral operators Example
- Assuming countable choice, counting measure is sigma-finite exactly on countable sets Example
- Assuming countable choice, zero on countable sets and infinity on cocountable sets is a non-semifinite measure Example
- Finite-rank truncations of a square-integrable kernel Example
- Integral operator trace under a valid diagonal hypothesis Example
- Multiplicity-two diagonal representation Example
- Pvm of a multiplication operator Example
- The square of the Volterra operator has zero trace Example
- FALSE: Tonelli's theorem still holds without any sigma-finiteness hypothesis False statement
- Assuming countable choice, an infinite-measure set in a semifinite measure space has arbitrarily large finite-measure subsets Lemma
- Complex Lq norm recovery from finite simple dual tests Lemma
- Finite-measure sets are approximable in measure by sets from a countable generating algebra Lemma
- For 1 ≤ p < ∞, every Lᵖ(μ) class has a sigma-finite essential support Lemma
- Product rectangle kernels are dense in product L two Lemma
- Sigma-finite ergodic oscillation sets have finite measure Lemma
- For sigma-finite measures, the section-measure functions are measurable Proposition
- Lebesgue measure is sigma-finite, and every metrically bounded subset of ℝⁿ has finite outer measure Proposition
- The functional Λ_g has norm ‖g‖_q; for q=∞ assume μ is semifinite Proposition
- Assuming countable choice, every measure is the sum of its semifinite part and a zero-infinity-valued measure Theorem
- Chain rule for a C¹ function with bounded derivative Theorem
- Chain rule for globally Lipschitz scalar maps of Sobolev functions Theorem
- Decomposable operators are the commutant of diagonal multiplication Theorem
- Direct integrals of measurable Hilbert fields are Hilbert spaces Theorem
- For 1 < p < ∞, the same representation theorem holds on arbitrary measure spaces Theorem
- For sigma-finite factors, the product measure exists, has the rectangle formula, is sigma-finite, and is unique Theorem
- For sigma-finite measures, the two section-measure integrals of a measurable set agree Theorem
- If μ is sigma-finite and A is countably generated, then Lᵖ(μ) is separable for 1 ≤ p < ∞ Theorem
- L two kernels give Hilbert–Schmidt operators Theorem
- Measurable essentially bounded operator fields act decomposably Theorem
- Measures agreeing on a generating pi-system are equal under an increasing finite-measure exhaustion from that pi-system Theorem
- On a sigma-finite measure space, every bounded linear functional on Lᵖ is integration against a unique L^q function Theorem
- Spectral multiplicity model for separably acting abelian von Neumann algebras Theorem
- Vitali convergence theorem on finite and sigma-finite measure spaces Theorem
Dependency tree · two levels
11 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- G. Folland, Real Analysis, 2nd ed., §1.3 (standard reference, not scraped)