Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
- Let be a natural number, let be an open subset of Euclidean space , let be the set of real numbers, let be a second-order equation operator on , and let . We say that is a…
Viscosity Subsolution and Supersolution of a Second-Order Equation
definitiondef:viscosity-sub-supersolution-2026bAnalysisPDELet be a natural number, let be an open subset of Euclidean space , let be the set of real numbers, let be the set of symmetric real matrices, let be a second-order equation operator on ,…First- and Second-Order Conditions at a Local Extremum of a Function of Class
lemmalem:c2-local-extremum-conditions-2026aAnalysisLinear AlgebraMultivariable CalculusLet be a natural number, let be an open subset of Euclidean space , let be the set of real numbers with the operations and the order of its ordered field structure, where for we write to mean t…Differences and Constants for Functions of Class on a Euclidean Open Set
lemmalem:c2-difference-constant-2026aAnalysisMultivariable CalculusLet be a natural number, let be an open subset of Euclidean space , and let be the set of real numbers with the operations and the order of its ordered field structure, where for we write to me…Euclidean Continuity Agrees with Metric Continuity for Real-Valued Functions
lemmalem:euclidean-metric-continuity-agree-2026aAnalysisTopologyMultivariable CalculusLet be a natural number, let be a subset of Euclidean space , let be the set of real numbers with the operations and the order of its ordered field structure, where for we write to mean that…Independence Fubini: Integration in an Independent Random Vector Given a Sub-Sigma-Algebra
lemmalem:independence-fubini-2026aAnalysisProbabilityLet be a probability space, let be a -algebra on with , let be a natural number, and let be measurable with respect to and the -fold…Cumulative-Rate Time Change: Regularity, Substitution, and Crossing Times
lemmalem:cumulative-rate-substitution-2026aAnalysisLet and be real numbers and let be measurable with respect to the trace Borel -algebra . Define the cumulative rate by the…Uniqueness of Finite Measures on a Generating Pi-System and the Density of the Exponential Law
lemmalem:finite-measure-uniqueness-2026aAnalysisProbability(Uniqueness) Let be a measurable space, let be a -system of subsets of whose generated -algebra is , and let and be measures on with and for every…- Let be a natural number and let be a real number. Write and for the -fold Borel -algebra and product Lebesgue measure on , and for the factorial. The ordered time simplex with horizon is t…
Assembly of Measure Spaces: Restriction, Transport, One-Point Spaces, and Countable Disjoint Unions
lemmalem:measure-space-assembly-2026aAnalysisMeasurability of maps between measurable spaces is that of Measurable Function and Real-Valued Measurable Function; measurability and integrals of -valued functions are those of Lebesgue Integral of a Nonnegative Measurable Function; measures use the conventions of…Finite Products of Lebesgue Measure and Coordinate Integration on
lemmalem:lebesgue-product-coordinate-integration-2026aAnalysisProbabilityLet be a natural number. Write for the Borel -algebra on the real numbers and for Lebesgue measure on it. Members of the -fold Cartesian product are written as tuples , and f…Image Measures, Measures with Densities, and Change of Variables
lemmalem:image-measure-density-2026aAnalysisProbabilityLet be a measure space and let be a measurable space. Measurability of maps between measurable spaces is that of Measurable Function and Real-Valued Measurable Function; measurability and integrals of -valued functions are those…- Let be a natural number, let be an open subset of Euclidean space , let be the set of real numbers, let be the set of symmetric real matrices, let be a second-order equation operator on ,…
Classical Subsolution and Supersolution of a Second-Order Equation
definitiondef:classical-sub-supersolution-2026bAnalysisPDELet be a natural number, let be an open subset of Euclidean space , let be the set of real numbers with the order of its ordered field structure, let be the set of symmetric real matrices,…- Let be a natural number, let be an open subset of Euclidean space , let be the set of real numbers with the order of its ordered field structure, let be the…
Degenerate Elliptic Second-Order Equation Operator
definitiondef:degenerate-elliptic-operator-2026aAnalysisPDELet be a natural number, let be an open subset of Euclidean space , let be the set of real numbers with the order of its ordered field structure, let be the…Second-Order Equation Operator on a Euclidean Open Set
definitiondef:second-order-equation-operator-2026aAnalysisPDELet be a natural number, let be an open subset of Euclidean space , let be the set of real numbers, and let be the set of symmetric real matrices. We write…Gradient of a Real-Valued Function on a Euclidean Open Set
definitiondef:gradient-euclidean-open-set-2026aAnalysisMultivariable CalculusLet be a natural number, let be an open subset of Euclidean space , let be the set of real numbers, let , and let . Assume that for every the partial derivative of with respe…Monotonicity of Squaring on the Nonnegative Elements of an Ordered Field
lemmalem:squares-monotone-nonnegative-2026aAnalysisAlgebraLet together with be an ordered field, with additive identity , and for let denote the associated strict order, that is, together with . For write for . Let satisfy…- Let be a natural number, let be an open subset of Euclidean space , and let . Let with , addition and scalar multiplication of points of being the coord…