Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Contraction Mapping Theorem on a Nonempty Complete Metric Space
theoremthm:contraction-mapping-complete-metric-space-2026bAnalysisTopologyLet be a complete metric space, and suppose that is nonempty. Let be a contraction. Then has a unique fixed point in . Moreover, for every , the iterated sequence converges to that fixed…- Let be a metric space, and let be a map. We say that is a contraction if there exists a real number satisfying such that for every .
- Let be a set, and let be a map. A point is called a fixed point of if
- Let be a metric space. We say that is complete if every Cauchy sequence in converges to a point of .
Orientable and Oriented Smooth Manifold with Boundary
definitiondef:oriented-smooth-manifold-boundary-2026aGeometryTopologyLet be a smooth manifold with boundary. We say that is orientable if it admits an oriented smooth atlas in the sense of Oriented Smooth Atlas on a Smooth Manifold with Boundary. An oriented smooth manifold with boundary is a smooth manifold with boundary together with a…Oriented Smooth Atlas on a Smooth Manifold with Boundary
definitiondef:oriented-smooth-atlas-manifold-boundary-2026aGeometryTopologyLet be a smooth manifold with boundary. An oriented smooth atlas on is a smooth atlas such that for every , the charts and are po…Positive Compatibility of Charts on the Interior of a Smooth Manifold with Boundary
definitiondef:positive-compatibility-charts-interior-manifold-boundary-2026aGeometryTopologyMultivariable CalculusLet be a smooth manifold with boundary of dimension , and let and be charts in the chosen smooth atlas. We say that these charts are positively compatible if either or else the following conditio…- Let be a topological space. We say that is second countable if there exists a basis for in the sense of Basis for a Topology such that is countable.
- Let be a topological space. A basis for the topology is a family with the following property: for every point and every open set satisfying , there exists a set…
- Let be a topological space. We say that is Hausdorff if for every two distinct points there exist open sets such that
Interior Points, Boundary Points, and Boundary of a Smooth Manifold with Boundary
definitiondef:boundary-smooth-manifold-with-boundary-2026aGeometryTopologyMultivariable CalculusLet be a smooth manifold with boundary of dimension in the sense of Smooth Atlas and Smooth Manifold with Boundary, and let . We say that is an interior point of if there exists a chart in the chosen atlas with and…Smooth Atlas and Smooth Manifold with Boundary
definitiondef:smooth-manifold-with-boundary-2026aGeometryTopologyMultivariable CalculusLet be a topological space, and let . A smooth atlas of dimension on , modeled on the closed upper half-space, is a family of charts for some set such that the follo…Smooth Compatibility of Charts Modeled on the Closed Upper Half-Space
definitiondef:smooth-compatible-charts-upper-half-space-2026aGeometryTopologyMultivariable CalculusLet be a topological space, let , and let and be charts of dimension on in the sense of Chart Modeled on the Closed Upper Half-Space. Write…Chart Modeled on the Closed Upper Half-Space
definitiondef:chart-upper-half-space-2026aGeometryTopologyMultivariable CalculusLet be a topological space, let , and let . A chart of dimension on , modeled on the closed upper half-space, is a pair with the following properties. 1. . 2. If denotes the half-space fr…Closed Upper Half-Space in Euclidean Space
definitiondef:closed-upper-half-space-euclidean-2026aGeometryTopologyMultivariable CalculusLet . In the Euclidean space , the closed upper half-space is the subset A subset is said to be open in if there exists an open subset suc…- Let be a metric space, let , and let satisfy . Then the open ball is open in the metric space .
- Let , and let . Then the following are equivalent. 1. is compact in , where is regarded as a topological space through the topology determined by the Euclidean distance. 2. is closed in a…
Compact Subset of is Closed
theoremthm:compact-subset-rn-closed-2026aAnalysisTopologyMultivariable CalculusLet , and let . Assume that is compact in , where is regarded as a topological space through the topology determined by the Euclidean distance. Then is closed in .Compact Subset of is Bounded
theoremthm:compact-subset-rn-bounded-2026aAnalysisTopologyMultivariable CalculusLet , and let . Assume that is compact in , where is regarded as a topological space through the topology determined by the Euclidean distance. Then is bounded as a subset of the metric space…Closed Box in is Compact
theoremthm:closed-box-compact-rn-2026aAnalysisTopologyMultivariable CalculusLet . For each index , let satisfy , and let be the closed box determined by these endpoints. Then is compact in , where is regarded as a topological sp…