Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Viscosity Inequalities Pass to Limits of Test-Function Data
lemmalem:viscosity-inequality-limit-test-data-2026bAnalysisPDEIf a second-order equation operator is continuous at a quadruple that is approximable by test data from above for a viscosity subsolution, the subsolution inequality holds at that quadruple; symmetrically from below for a supersolution.The Set of Symmetric Real Matrices is a Metric Space
lemmalem:symmetric-matrix-distance-is-metric-2026aAnalysisTopologyLinear AlgebraLet be a natural number, let be the set of symmetric real matrices, and let be the distance between symmetric real matrices. Then is a metric on , so that…Distance Between Symmetric Real Matrices
definitiondef:symmetric-matrix-distance-2026aAnalysisLinear AlgebraLet be a natural number, let be the real numbers, and let be the set of symmetric real matrices. For the difference is again symmetric by claim 1 of…A Sum in Separated Variables of Semiconvex Functions is Semiconvex
lemmalem:separated-sum-semiconvex-2026aAnalysisPDELet and be natural numbers and let be the real numbers with the order of their ordered field structure. For a natural number regard Euclidean space as a real vector space, with the sum of points, the scalar multiple and the…Perturbation Splitting of a Quadratic Form
lemmalem:quadratic-form-perturbation-split-2026aAnalysisLinear AlgebraPDELet be a natural number and let be the real numbers with the order of their ordered field structure. On Euclidean space , a real vector space, write for the sum of points, and for the difference and dot product,…Hessian Lower Bound for a Test Function Touching a Semiconvex Function from Above
lemmalem:semiconvex-upper-test-hessian-bound-2026aAnalysisPDEMultivariable CalculusLet be a natural number and let be the real numbers with the order of their ordered field structure. Regard Euclidean space as a real vector space, with the sum of points, the scalar multiple, and the…Restriction of a Map to an Open Subset
lemmalem:ck-restriction-open-subset-2026aMultivariable CalculusLet be natural numbers and let be the real numbers. Let be an open subset of Euclidean space and let be open in . Let and , and let…Transfer of a Test Function from the Sup-Convolution to the Original Function
lemmalem:sup-convolution-test-transfer-2026aPDELet , , and be as in Sup-Convolution of a Function on ; regard as a real vector space, with the sum of points, the scalar multiple and the difference . Let be the Euclidean distance, a…The Sup-Convolution Converges Pointwise to an Upper Semicontinuous Function
theoremthm:sup-convolution-pointwise-convergence-2026aAnalysisLet , , and be as in Sup-Convolution of a Function on , and let be the Euclidean distance, a metric on . Let be upper semicontinuous on with…The Sup-Convolution of an Upper Semicontinuous Function Attains its Supremum
lemmalem:sup-convolution-maximizer-2026aAnalysisLet , , and be as in Sup-Convolution of a Function on , and let be the Euclidean distance, a metric on . Let be upper semicontinuous on with…Domination, Monotonicity and Semiconvexity of the Sup-Convolution
lemmalem:sup-convolution-basic-properties-2026aAnalysisLet , , and be as in Sup-Convolution of a Function on , and let denote the dot product of points of . The set is a convex subset of itself, directly from that definit…- Let be a natural number with and let be the real numbers, a Dedekind complete ordered field, with the order , the strict order and the quotient notation fixed there; write for the real number , which satisfies by claim 8 of…
- Let be a natural number with , let be the real numbers with the order of their ordered field structure, write to mean that and , let be the absolute value of , and let be the metric on of…
- Let be a natural number with , let be the real numbers with the order of their ordered field structure, and write to mean that and . Regard Euclidean space as a real vector space, with the sum of points and th…
Quadratic Increment Characterisation of Semiconvexity
lemmalem:semiconvex-quadratic-inequality-2026aAnalysisLet be a natural number with and let be the real numbers with the order of their ordered field structure; write for , which satisfies and therefore has a multiplicative inverse by claim 8 of…The Squared Norm of a Convex Combination of Two Points
lemmalem:norm-convex-combination-identity-2026aLinear AlgebraLet be a natural number with , let be the real numbers with the order of their ordered field structure, and for a real number write for the power . Regard Euclidean space as a real vector space, with the sum of…Mollification Converges Uniformly on Compact Subsets
theoremthm:mollification-uniform-convergence-compact-2026aAnalysisLet be a natural number with , let be the real numbers with the order of their ordered field structure, write to mean that and , write for the multiplicative inverse of , let be the absolute value of …Uniform Continuity Along a Compact Subset of the Domain
lemmalem:uniform-continuity-near-compact-2026aTopologyLet be a metric space, equipped with the collection of all subsets open in , which is a topology by Metric Open Sets Form a Topology. Let be the real numbers with the order of their ordered field structure, write to mean that and…A Compact Subset of an Open Set Admits a Uniform Ball Radius
lemmalem:compact-in-open-positive-distance-2026aTopologyLet be a metric space, equipped with the collection of all subsets open in , which is a topology by Metric Open Sets Form a Topology. Let be the real numbers. Write for the closed ball in with centre and radius . Let…- Let be a natural number with , let be the real numbers, and let satisfy and . Write for the multiplicative inverse of , and let powers with a natural exponent be those of…