Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Derivative of a Polynomial Function on the Real Line
lemmalem:polynomial-derivative-real-2026aAnalysisLet be the real numbers and let be the set of natural numbers, with successor map as in that definition. Let be the canonical map of , as in clause 3 of The Real Numbers and Standard Notation (…Constants, Powers, Sums, Scalar Multiples and Products of Polynomial Functions
lemmalem:polynomial-function-algebra-2026aAlgebraLet be a field, with additive identity and multiplicative identity , and let be the set of natural numbers. Let be polynomial functions on and let . Write , and for the pointwise sum, scalar multiple and…- Let be a field. A map is a polynomial function on if there are a natural number , an element , and a map on the initial segment determined by , with values written , such that…
Addition of Exponents for Natural Number Powers in a Field
lemmalem:natural-power-exponent-addition-2026aAlgebraLet be a field, let , and let be the set of natural numbers, with addition as in that definition. Powers are those of Natural Number Power of an Element of a Field. ThenCoordinatewise Criterion for Continuity of a Map Between Euclidean Spaces
lemmalem:continuity-coordinatewise-euclidean-2026aAnalysisMultivariable CalculusLet and be natural numbers, let be the real numbers, let be a subset of Euclidean space , let with coordinate functions , and let . Each is regarded as a map from int…Composites of Cᵏ Functions Are of Class Cᵏ
theoremthm:ck-composition-euclidean-2026bAnalysisMultivariable CalculusThe partial derivatives of a composite g∘f of C¹ functions are given by the chain rule, and composites of Cᵏ, respectively smooth, functions between open subsets of Euclidean spaces are Cᵏ, respectively smooth.Constants, Affine Functions, Sums, Products and Quotients of Cᵏ Functions
lemmalem:ck-algebra-euclidean-2026bAnalysisMultivariable CalculusConstant, affine and coordinate functions are smooth, and sums, scalar multiples, products, reciprocals and quotients (with nonvanishing denominator) of Cᵏ, respectively smooth, functions on U are again Cᵏ, respectively smooth.Convolution with a Kernel is of Class
theoremthm:convolution-smooth-2026aAnalysisMultivariable CalculusLet , , , , , the set and the convolution be as in Convolution of a Continuous Function with a Compactly Supported Continuous Kernel. By claim 2 of Differentiating a Convolution through the Kernel the set is…Differentiating a Convolution through the Kernel
lemmalem:convolution-partial-derivative-2026aAnalysisMultivariable CalculusLet , , , , , the set and the convolution be as in Convolution of a Continuous Function with a Compactly Supported Continuous Kernel, let be the Euclidean norm on and let denote the…Partial Derivatives, Continuity and Regularity under a Scaling Substitution
lemmalem:partial-derivative-affine-substitution-2026aAnalysisMultivariable CalculusLet be natural numbers and let be the real numbers, with absolute value . Regard Euclidean space as a real vector space, and let be the Euclidean norm and the Euclidean distance, a metric on .…Progressive Measurability: Sections, Right-Continuous Adapted Processes, Arithmetic, and Indefinite Time Integrals
lemmalem:progressive-measurability-toolkit-2026aProbabilityLet be the real numbers, let be a probability space, let be real, and let be a filtration on with time index restricted to . Progressive measurability of a family…- Let be a probability space, let be a real number, and let be a filtration on with time index restricted to . For let be the trace Borel -algebra…
Arithmetic of Measurable Real- and [0,∞]-Valued Maps
lemmalem:measurable-real-arithmetic-2026bAnalysisSums, differences, multiples, products, absolute values, maxima, minima, positive and negative parts and finite sums of measurable real-valued maps are measurable, and so are sums, multiples and products of measurable [0,∞]-valued maps.Existence and Equality of the Reversed Mixed Second Partial Derivative
theoremthm:mixed-partials-symmetry-existence-2026aAnalysisMultivariable CalculusLet be a natural number, let be the real numbers, let be an open subset of Euclidean space , let , let , and let and satisfy and , index ranges using the order on the natural numbers…Multi-Index Partial Derivatives of a Map and of a Smooth Map
theoremthm:ck-multi-index-partials-2026aAnalysisMultivariable CalculusLet and be natural numbers, let be the real numbers, let be an open subset of Euclidean space , let have coordinate functions , and let be a multi-index of length , of…Basic Properties of Cᵏ Functions
lemmalem:ck-map-basic-properties-2026bAnalysisMultivariable CalculusClass Cᵏ⁺¹ implies class Cᵏ; the partial derivatives of a Cᵏ⁺¹ (smooth) real function are Cᵏ (smooth); Cᵏ functions are continuous; and C¹ functions are differentiable with continuous gradient, respectively Jacobian matrix.Peeling the Innermost Variable from a Multi-Index Partial Derivative
lemmalem:multi-index-partial-innermost-2026aAnalysisMultivariable CalculusLet be a natural number, let be the real numbers, let be an open subset of Euclidean space , and let . Let be a multi-index of length with , with the zero multi-index , t…Jacobian Determinant on a Euclidean Open Set
definitiondef:jacobian-determinant-euclidean-2026aAnalysisLinear AlgebraMultivariable CalculusLet be a natural number, let be the real numbers, let be an open subset of Euclidean space , let , and let . Suppose that the Jacobian matrix is defined; it is then a real matrix with rows and colu…Partial Derivative of a Multi-Index on a Euclidean Open Set
definitiondef:partial-derivative-multi-index-2026aAnalysisMultivariable CalculusLet and be natural numbers, let be the real numbers, let be an open subset of Euclidean space , and let be a multi-index of length , with the zero multi-index , the standard basis multi-indices…Smooth Functions on an Open Subset of ℝⁿ
definitiondef:smooth-map-euclidean-2026cAnalysisMultivariable CalculusA real- or vector-valued function on an open subset U of ℝⁿ is smooth on U if it is of class Cᵏ on U for every k in ℕ₀.