Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Sum and Product Rules for One-Dimensional Derivatives and Continuity
lemmalem:derivative-continuity-rules-1d-2026aAnalysisLet be an interval, let , and let be a real number. Here , , and denote the pointwise sum, scalar multiple, and product. 1. (Differentiability implies continuity) If is an interior point of and is differentiable at…Gaussian Process Characterization of Standard Brownian Motion
lemmalem:brownian-motion-gaussian-characterization-2026cProbabilityLet be a probability space and let be a stochastic process on indexed by the nonnegative real numbers, being the real numbers. For real numbers and , let denote the smaller of …Pairwise Uncorrelated Jointly Gaussian Random Variables are Independent
corollarycor:uncorrelated-gaussian-mutual-independence-2026aProbabilityLet be a probability space, let be a natural number, and let be a Gaussian random vector on whose distinct components are pairwise uncorrelated: with the covariance of square-integrable random variables, defi…Independent Gaussian Random Variables are Jointly Gaussian
lemmalem:independent-gaussians-jointly-gaussian-2026aProbabilityLet be a probability space, let be a natural number, and let be independent random variables on , each of which is a Gaussian random variable. Then is a Gaussian random vector, and its distinct…- Let be a probability space and let be the real numbers. A stochastic process on , indexed by the nonnegative real numbers, is a standard Brownian motion if: (i) (Initial value) almost surely (t…
Conditional Expectation Given Countably Many Jointly Gaussian Observations
theoremthm:gaussian-conditional-expectation-countable-2026aProbabilityLet and () be random variables on a probability space such that the family is jointly Gaussian. Write, with the generated -algebras,…Jointly Gaussian Families of Random Variables and Gaussian Processes
definitiondef:gaussian-family-2026aProbabilityLet be a probability space, let be a nonempty set, and let be a family of random variables on . The family is jointly Gaussian (a Gaussian family) if for every natural number and all disti…Conditional Expectation for Jointly Gaussian Random Variables is Affine
theoremthm:gaussian-conditional-expectation-affine-2026aProbabilityLet be a natural number and let be a Gaussian random vector on a probability space . Then there exist real numbers such that the random variable has the foll…Uncorrelated Jointly Gaussian Blocks are Independent
theoremthm:gaussian-uncorrelated-independent-2026aProbabilityLet and be natural numbers and let be a Gaussian random vector on a probability space such that, with the covariance of square-integrable random variables (defined and finite by…Gram-Schmidt Orthonormalization of a Finite Family of Vectors
lemmalem:gram-schmidt-2026aLinear AlgebraLet and be natural numbers and let be vectors in the Euclidean space , with the dot product. Then either every is the zero vector, or there exist a natural number and an orthonormal family in …Alignment of Orthonormal Families by Plane Rotations
theoremthm:orthonormal-alignment-2026aLinear AlgebraLet and be natural numbers and let be an orthonormal family in the Euclidean space , with standard basis vectors . Then: 1. . 2. There exist a finite composition of plane rotations of and a sign…- Let be a natural number with and let be a plane rotation of the Euclidean space . Then for all , with the dot product, Consequently, every finite composition of plane rotations satisfies…
Orthonormal Families, Standard Basis Vectors, and Plane Rotations of Euclidean Space
definitiondef:orthonormal-plane-rotation-2026aLinear AlgebraLet be a natural number and let be Euclidean space with the dot product . Orthonormal family. Vectors (with a natural number) form an orthonormal family if…Orthonormal Linear Combinations of Independent Standard Normal Random Variables
theoremthm:orthonormal-normal-combinations-2026aProbabilityLet and be natural numbers, let be independent standard normal random variables on a probability space , and let , with coordinates , be an orthonormal family in the Euclidean space…Plane Rotations Preserve Independent Standard Normal Families
lemmalem:plane-rotation-normal-family-2026aProbabilityLet be a natural number with , let be independent standard normal random variables on a probability space , let , and let be real numbers with . Define…Rotation Invariance of a Pair of Independent Standard Normal Random Variables
lemmalem:gaussian-rotation-invariance-2026aProbabilityLet and be independent standard normal random variables on a probability space , and let and be real numbers with . Then are independent standard normal random variables o…Translation Invariance of Lebesgue Measure and the Lebesgue Integral
lemmalem:lebesgue-translation-invariance-2026aAnalysisProbabilityFor a subset of the real line and a real number , write . Let be the Lebesgue outer measure, Lebesgue measure, and the Borel -algebra. Then for every real : 1. (Sets) For every…Standardization and Cumulative Distribution Function of a Gaussian Random Variable
lemmalem:gaussian-cdf-2026bProbabilityLet be a Gaussian random variable on a probability space , with mean and variance , both defined and finite by Square-Integrability, Moments, and Covariance Matrix of a Gaussian Random Vector. Then:…Reflection Invariance of Lebesgue Measure and Symmetry of the Standard Normal Distribution
lemmalem:standard-normal-symmetry-2026aAnalysisProbabilityFor a subset of the real line write . Let be the Lebesgue outer measure, Lebesgue measure, the Borel -algebra, and the standard normal distribution. Then:…Covariance of Square-Integrable Random Variables
definitiondef:covariance-square-integrable-2026aProbabilityLet be a probability space and let and be square-integrable random variables on it. The covariance of and is This is defined: square-integrable random…