Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Jensen's Inequality for Finite Convex Combinations
theoremthm:jensen-inequality-finite-2026aAnalysisMultivariable CalculusLet and be natural numbers with and , let be the real numbers with the order of its ordered field structure, and let be the initial segment determined by . Let be a convex subset of Euclidean space , regarded…Properties of the Norm of a Symmetric Real Matrix
lemmalem:symmetric-matrix-norm-properties-2026aAnalysisLinear AlgebraMultivariable CalculusLet be a natural number with and let be the real numbers with the order of its ordered field structure and the absolute value . Let and be symmetric real matrices and let . Write for the…Small Cases, Reduction, and Membership for Convex Combinations
lemmalem:convex-combination-properties-2026aAnalysisLinear AlgebraMultivariable CalculusLet and be natural numbers with and , let be the real numbers with the order of its ordered field structure, and for a natural number let be the initial segment determined by . Regard Euclidean space as a rea…A Closed Euclidean Ball is Convex and Compact
lemmalem:closed-euclidean-ball-convex-compact-2026aAnalysisTopologyMultivariable CalculusLet be a natural number with , let be the real numbers with the order of its ordered field structure, let be a point of Euclidean space , regarded as a real vector space by Euclidean Space is a Real Vector Space, and…- Let be a natural number with and let be a symmetric real matrix. On Euclidean space write for the dot product, for the Euclidean norm of a point , and for the matrix-vector product; let…
Testing a Block Semidefinite Inequality on the Diagonal
lemmalem:block-order-implies-matrix-order-2026aAnalysisLinear AlgebraMultivariable CalculusLet be a natural number with , let be the real numbers, let , and let and be symmetric real matrices. Write for the identity matrix of size , write for the real matrix all of whose entrie…Elementary Properties of the Closed Ball in a Metric Space
lemmalem:closed-ball-properties-metric-2026aAnalysisTopologyLet be a metric space, let , let be a real number with , the order being that of the ordered field of real numbers, and let be the closed ball. Let be the collection of subsets of that are open in , a t…The Quadratic Form of a Real Square Matrix is Bounded on the Closed Unit Ball
lemmalem:matrix-quadratic-form-bounded-2026aAnalysisLinear AlgebraMultivariable CalculusLet be a natural number with , let be the initial segment determined by , and let be the real numbers with the order of its ordered field structure and the absolute value . Let be a real matrix, with entries…The Positive Semidefinite Ordering is a Partial Order Compatible with the Linear Structure
lemmalem:psd-ordering-partial-order-2026aAnalysisLinear AlgebraLet be a natural number with , let be the initial segment determined by , and let be the real numbers with the order of its ordered field structure. Let , and be symmetric real matrices and let . Wri…Action and Quadratic Form of a Block Matrix
lemmalem:block-matrix-quadratic-form-2026aAnalysisLinear AlgebraMultivariable CalculusLet and be natural numbers with and , let be the real numbers, and for a natural number let be the initial segment determined by . Let , , and be real matrices of sizes , , and…Convex Combination of Finitely Many Points of
definitiondef:convex-combination-rn-2026aAnalysisLinear AlgebraMultivariable CalculusLet and be natural numbers with and , let be the real numbers with the order of its ordered field structure, and let and be the initial segments determined by and by . Let be a family of points…- Let be a metric space, let , and let be a real number with , the order being that of the ordered field of real numbers. The closed ball in with centre and radius is the subset
Block Matrix with Two Row Blocks and Two Column Blocks
definitiondef:block-matrix-2x2-2026aLinear AlgebraLet and be natural numbers with and , let be the real numbers, and for a natural number let be the initial segment determined by . Let , , and be real matrices of sizes , , and…Comparison and Absolute Value Bounds for Finite Sums of Real Numbers
lemmalem:finite-sum-comparison-absolute-2026aAnalysisAlgebraLet be the real numbers, an ordered field with additive identity and order , and write for the absolute value of . Let be a natural number, let be the initial segment determined by , and let and…- Let be the set of real numbers, with the order of its ordered field structure. A subset is order-convex if for all and every with and , one has
- Let be the set of real numbers, with the order of its ordered field structure, and let . The closed interval with endpoints and is the subset
A Function of Class with Positive Semidefinite Hessian is Convex
theoremthm:hessian-psd-implies-convex-2026aAnalysisLinear AlgebraMultivariable 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, and let be…A Real Function with Nonnegative Second Derivative is Convex on an Interval
theoremthm:second-derivative-nonnegative-convex-1d-2026aAnalysisLet be the real numbers and let be the real line. Let be order-convex and such that every satisfies for some , so that every point of is an interior point of . Let…Derivatives of the Slice of a Function Along a Line
lemmalem:line-slice-derivative-2026bAnalysisMultivariable CalculusLet be a natural number, let be the real numbers, and let be an open subset of Euclidean space . Write for the dot product of points of and for the matrix-vector product. Let be…Derivative of a Finite Linear Combination of Real Functions
lemmalem:derivative-finite-linear-combination-2026aAnalysisLet be the real numbers, let be order-convex, and let satisfy for some , so that is an interior point of and derivatives at in the sense of Derivative at an Interior Point are defined. Let be…