Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Reduction of the Theorem on Sums to a Global Quadratic Bound
lemmalem:theorem-on-sums-reduction-2026aAnalysisPDENormalises the data of the theorem on sums by translation and an affine correction and localises the summands to a closed ball, producing upper semicontinuous functions bounded above on the whole space that vanish at the origin, satisfy a global quadratic bound with matrix…The Theorem on Sums for a Global Quadratic Bound, in Two Groups of Variables
theoremthm:theorem-on-sums-global-quadratic-2026aAnalysisPDEFor upper semicontinuous functions bounded above, vanishing at the origin and satisfying globally, produces for each symmetric matrices that are admissible second-order test d…Second-Order Test Data at a Global Quadratic Maximum of a Semiconvex Function
lemmalem:semiconvex-quadratic-maximum-hessian-2026aAnalysisPDEFor a semiconvex function on whose difference with a quadratic form attains a maximum at the origin, produces points of twice differentiability approaching the origin whose gradients tend to zero and whose Hessians converge to a symmetric matrix with…Transfer of Approximating Test Data from the Sup-Convolution to the Original Function
lemmalem:sup-convolution-test-data-transfer-2026aAnalysisPDEShows that test data approximable from above for the sup-convolution at a point with first-order datum transfers to the same first-order and second-order data for itself at , together with the accompanying identity for the…Quadratic Test Functions, Limits, Translation and Locality for Approximability by Test Data
lemmalem:test-data-basic-2026aAnalysisPDEApproximability by test data can always be realised with quadratic test functions; it follows at a point of twice differentiability, is stable under limits of the approximating data, transforms predictably under translation and affine perturbation, and depends only on the values…Jensen's Lemma: the Contact Set of a Semiconvex Function at a Strict Maximum has Positive Measure
lemmalem:jensen-maximum-2026aAnalysisPDEMultivariable CalculusFor a semiconvex function with a strict maximum at the centre of a closed ball, the set of points at which some linear perturbation of norm at most attains its maximum is compact of positive Lebesgue measure for all small , so it is contained in no null set, and…- Standing hypotheses for a nonempty bounded open subset of Euclidean space: its closure is compact, and its boundary is the complement of the domain in the closure.
- Standing notation and background facts for second-order equations on open subsets of Euclidean space: the reals, Euclidean space with its metric and topology, symmetric matrices with the positive semidefinite ordering, functions of class with their gradients and Hessians, a…
- Given upper semicontinuous summands on open sets and a test function whose difference with their sum has a local maximum, produces for each symmetric matrices that are admissible second-order test data from above for the summands, with block diagon…
Quadruple Approximable by Test-Function Data
definitiondef:approximable-by-test-data-2026aAnalysisPDEA quadruple of a point, value, vector and symmetric matrix is approximable by test data when it is the limit of data of test functions touching the function from above (or from below) at nearby points.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.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…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…A Semiconvex Function of Class has Hessian Bounded Below by
corollarycor:semiconvex-c2-hessian-bound-2026aAnalysisPDEMultivariable CalculusLet be a natural number and let be the real numbers. Let be an open and convex subset of Euclidean space , a real vector space by Euclidean Space is a Real Vector Space, let satisfy…Semiconvex Function on a Convex Subset of
definitiondef:semiconvex-function-rn-2026aAnalysisPDEMultivariable CalculusLet be a natural number, let be the real numbers, let be convex, let , and let satisfy . Write for the Euclidean norm on . We say that is…Comparison Principle for First-Order Strictly Proper Equations by Doubling of Variables
theoremthm:comparison-first-order-strictly-proper-2026bAnalysisPDEDoubling of variables yields comparison on a bounded domain for a strictly proper operator that does not depend on the matrix argument and satisfies a structure condition with a modulus of continuity.Comparison of a Viscosity Subsolution with a Strict Classical Supersolution
theoremthm:comparison-c2-strict-supersolution-2026bAnalysisPDEOn a bounded domain, a viscosity subsolution of a proper operator lies below any lower semicontinuous strict classical supersolution that dominates it on the boundary.Viscosity Subsolution and Supersolution up to the Boundary
definitiondef:viscosity-sub-supersolution-boundary-2026bAnalysisPDEA function on the closure of an open set is a viscosity sub- or supersolution up to the boundary when it is semicontinuous on the closure and its restriction to the open set is a viscosity sub- or supersolution there.