Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Existence and Uniqueness for Ordinary Differential Equations with Measurable Time Dependence
theoremthm:caratheodory-ode-2026cAnalysisFor a right-hand side that is measurable in time, Lipschitz in the state with constant Λ and integrable at the origin, the integral equation on [a,b] has exactly one Carathéodory solution for each initial value; it is continuous, obeys an exponential a priori bound, depends on th…Norm Bound for a Vector-Valued Lebesgue Integral over a Compact Interval
lemmalem:vector-integral-norm-bound-2026aAnalysisLet be a natural number, let be real numbers, and let be a map into Euclidean space whose components are bounded and measurable with respect to the trace Borel -algebra on and the Borel -algebra on the…- A bounded measurable function on [a,b] satisfying a linear integral inequality with a nonnegative coefficient is bounded by the corresponding exponential.
Nearest-Point Projection onto a Nonempty Closed Convex Subset of Euclidean Space
lemmalem:convex-projection-rn-2026aAnalysisLet be a natural number and let be a nonempty subset of Euclidean space that is convex and closed for the topology of open subsets determined by the Euclidean distance. Write for the dot product of and for the…Suprema, Infima, Limits Inferior and Limits Superior of Measurable [0,∞]-Valued Maps
lemmalem:measurable-limits-toolkit-2026dAnalysisProbabilityCountable suprema and infima, limits inferior and limits superior of a sequence of measurable [0,∞]-valued maps are measurable.- Defines a map between metric spaces to be Lipschitz with constant L when it multiplies distances by at most L, and Lipschitz when some such nonnegative constant exists.
Below-Frontier Evaluations, Tilted Poisson Moment Functions, and Multi-Base Window Bounds for Jointly Driven Solutions of the Controlled N-Agent Dynamics
lemmalem:n-agent-multibase-window-2026bProbabilityAdopt the setting, notation, and hypotheses of Level-Revealed Conditioning for Jointly Driven Solutions of the Controlled N-Agent Dynamics --- in particular the -algebra and the independence of the finite family consisting of together with…Interior Points in the Metric Topology are Exactly the Centres of Contained Closed Balls
lemmalem:interior-metric-closed-ball-criterion-2026aAnalysisTopologyLet be a metric space and let be the collection of the subsets of that are open in the metric space ; by The Open Subsets of a Metric Space Form a Topology the pair is a topological space, and interiors below are taken in…A Convex Function is Continuous near an Interior Point
corollarycor:convex-function-continuous-near-interior-point-2026aAnalysisMultivariable CalculusLet , , , , the Euclidean norm , the Euclidean metric and the closed balls of Closed Ball in a Metric Space be as in A Convex Function is Lipschitz on a Ball around an Interior Point. Regard…A Convex Function is Lipschitz on a Ball around an Interior Point
theoremthm:convex-function-lipschitz-near-interior-point-2026aAnalysisMultivariable CalculusLet be a natural number with , let be the initial segment determined by , and let be the set of real numbers with the operations and the order of its ordered field structure, with the absolute value written . On Euclidean space…Increment Bound for a Convex Function through an Extended Point
lemmalem:convex-function-increment-bound-2026aAnalysisMultivariable CalculusLet be a natural number with , let be the set of real numbers with the operations and the order of its ordered field structure, let be a convex subset of Euclidean space , a real vector space by…A Convex Function Bounded Above on a Set Symmetric about a Point is Bounded Below on It
lemmalem:convex-function-bounded-below-reflection-2026aAnalysisMultivariable CalculusLet be a natural number with , let be the set of real numbers with the operations and the order of its ordered field structure, let be a convex subset of Euclidean space , a real vector space by…A Convex Function is Bounded Above near a Point by its Values at Coordinate Neighbours
lemmalem:convex-function-bounded-above-crosspolytope-2026aAnalysisMultivariable CalculusLet be a natural number with , let be the initial segment determined by , and let be the set of real numbers with the operations and the order of its ordered field structure, with the absolute value written . Let be a convex su…Determinant Bound for a Matrix Squeezed between a Negative Multiple of the Identity and Zero
corollarycor:determinant-bound-semidefinite-interval-2026aAnalysisLinear AlgebraLet be a natural number, let be the initial segment determined by , and let be the set of real numbers with the operations and the order of its ordered field structure, with the absolute value written . Let with…Hadamard's Inequality for a Positive Semidefinite Matrix
theoremthm:hadamard-determinant-inequality-psd-2026aAnalysisLinear AlgebraLet be a natural number, let be the initial segment determined by , let be the set of real numbers with the operations and the order of its ordered field structure, and let be a symmetric positive semidefinite real matrix, with entr…The Determinant of a Triangular Matrix is the Product of its Diagonal Entries
lemmalem:determinant-triangular-2026bAlgebraLinear AlgebraIf all entries of a square real matrix above the diagonal, or all entries below it, are zero, its determinant is the product of its diagonal entries.- The determinant of a product of two square real matrices is the product of their determinants.
Rules for the Determinant: Rows, Scalar Multiples and the Transpose
lemmalem:determinant-row-properties-2026bAlgebraLinear AlgebraThe determinant of the identity is 1; the determinant is linear in each row, changes by the sign under a permutation of the rows, vanishes when two rows agree, a row is zero or the rows are linearly dependent, scales by the n-th power under scalar multiples, and is unchanged by t…- The sign of a permutation of [n] is 1 or -1; it is 1 at the identity, multiplicative under composition, unchanged by inversion, and -1 at every transposition.
An Injective Self-Map of a Finite Set is a Bijection
lemmalem:injective-self-map-finite-set-bijective-2026aCombinatoricsSet TheoryLet be the set of natural numbers with successor map as in that definition, let , and let be the initial segment determined by . Call a map between sets injective if implies for all . The notions…