Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Riesz-Markov Representation Theorem on a Compact Metric Space
theoremthm:riesz-markov-compact-metric-2026aAnalysisTopologyLet be a metric space with nonempty, let be the collection of subsets of that are open in , which is a topology on by Metric Open Sets Form a Topology, and assume that is compact in . Let be the…A Countable Uniformly Dense Family of Lipschitz Functions on a Compact Metric Space
lemmalem:continuous-uniform-dense-compact-2026aAnalysisTopologyLet be a metric space with nonempty, and let be the collection of subsets of that are open in , which is a topology on by Metric Open Sets Form a Topology. Assume that is compact in . Let denote the…Continuous Partition of Unity Subordinate to a Finite Open Cover of a Compact Set in a Metric Space
lemmalem:partition-of-unity-compact-metric-2026aAnalysisTopologyLet be a metric space, and let be the collection of subsets of that are open in , which is a topology on by Metric Open Sets Form a Topology. Let denote the real numbers, with the addition, multiplication, identities, additive i…- Let be a natural number, let be the Euclidean norm on Euclidean space and let be the Euclidean distance, a metric on ; write for the closed ball of centre and radius in . Let…
A Continuous Compactly Supported Function on is Uniformly Continuous
lemmalem:continuous-compact-support-uniformly-continuous-2026aAnalysisTopologyLet be a natural number, let be the Euclidean norm on , and let denote the Euclidean distance, a metric on each Euclidean space. Let be continuous on , as a map from …The Borel -Algebras of Euclidean Space and of the Euclidean Metric Coincide
lemmalem:borel-metric-euclidean-agree-2026aAnalysisTopologyLet be a natural number and let be the Euclidean distance on Euclidean space , which is a metric. Then the Borel -algebra of the metric space and the Borel -algebra…- Let be a metric space with Borel -algebra . A Borel measure on is a measure on the measurable space .
Compact Support on Means Vanishing Outside a Bounded Set
lemmalem:compact-support-euclidean-criterion-2026aAnalysisTopologyLet be a natural number, let be the Euclidean norm on Euclidean space , and let be the Euclidean distance, a metric on . By Metric Open Sets Form a Topology the subsets open in form a topology on…Compactly Supported Real-Valued Function
definitiondef:compactly-supported-function-2026aAnalysisTopologyLet be a topological space and let . We say that is compactly supported if its support is a compact subset of .Support of a Real-Valued Function on a Topological Space
definitiondef:support-real-function-topological-2026aAnalysisTopologyLet be a topological space, let be the real numbers, and let . The support of , written , is the closure in of the setLipschitz Test Functions Determine a Finite Borel Measure, and Uniqueness of Weak Limits
lemmalem:weak-limit-unique-2026aAnalysisTopologyProbabilityLet be a metric space with nonempty and let be its Borel -algebra. Regard as a metric space with the absolute-value metric, and let bounded have the meaning fixed there for a real-valued function on a set. 1. (Determination) Let…- Let be a metric space with nonempty, let be its topology of open subsets, and let be its Borel -algebra. Let be a sequence of probability measures on and let be a probabilit…
Bounded Lower Semicontinuous Functions are Increasing Limits of Lipschitz Functions
lemmalem:lipschitz-approximation-lsc-2026aAnalysisTopologyLet be a metric space with nonempty, let be a real number with , and let be lower semicontinuous on with for every . For let , where is the canonical map from…Weak Convergence of Finite Borel Measures on a Metric Space
definitiondef:weak-convergence-measures-metric-2026aAnalysisTopologyProbabilityLet be a metric space, let be a sequence of Borel measures on with for every , and let be a Borel measure on with . Regard as a metric space with the absolute-value metric.…Borel Measurability and Bounded Integration on a Metric Space
lemmalem:borel-metric-toolkit-2026aAnalysisTopologyProbabilityLet be a metric space, let be its topology of open subsets, and let be its Borel -algebra. Measurability of maps between measurable spaces is that of Measurable Function and Real-Valued Measurable Function, and…- Let and be metric spaces and let be Lipschitz. Then is uniformly continuous on , and is continuous on .
Borel Sigma-Algebra of a Metric Space
definitiondef:borel-sigma-algebra-metric-2026aAnalysisTopologyProbabilityLet be a metric space. The Borel -algebra of , denoted , is the -algebra generated by the family of all open subsets of . Its members are called the Borel subsets of . When the metric is clear from the context we wri…Rational Intervals and Rays Generate the Borel Sigma-Algebra of the Real Line
lemmalem:borel-real-generators-2026aAnalysisTopologyLet be the set of rational numbers and let be the Borel -algebra on the real line. Write for the family of open intervals with and , and for the family of rays…Uniformly Equicontinuous Family of Maps Between Metric Spaces
definitiondef:uniformly-equicontinuous-family-2026aAnalysisTopologyLet and be metric spaces and let be a set of maps from to . The family is uniformly equicontinuous if for every real number there is a real number such that…Borel Sigma-Algebra on Euclidean Space
definitiondef:borel-sigma-algebra-euclidean-2026aAnalysisTopologyLet be a natural number. The Borel -algebra on Euclidean space , written , is the -algebra generated by the family of all Euclidean open subsets of ; its members are the Borel subsets of …