Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Square-Integrability, Moments, and Covariance Matrix of a Gaussian Random Vector
lemmalem:gaussian-moments-2026bProbabilityLet be a Gaussian random vector on a probability space and let be any Gaussian representation of it. Then: 1. (Square-integrability) Each is square-integrable. 2. (Moments) With the…Affine Transformations of Gaussian Random Vectors are Gaussian
lemmalem:gaussian-affine-transformation-2026bProbabilityLet be a Gaussian random vector on a probability space , let be a natural number, and let and (, ) be real numbers. Define Then…Gaussian Random Vectors and Jointly Gaussian Random Variables
definitiondef:gaussian-random-vector-2026bProbabilityLet be a probability space and let be a natural number. Random variables on are jointly Gaussian, and the tuple is called a Gaussian random vector, if there exist , either zero or a…Generated Sigma-Algebras Need Not Converge in Mean Square under Convergence of the Generating Random Variables
propositionprp:generated-sigma-algebras-nonconvergence-2026aProbabilityThere exist a probability space , random variables and on it, and a sequence of random variables on it with the following properties, where denotes the -algebra generated by a random variable, measur…Joint Continuity of Conditional Expectation under Mean-Square Convergence
lemmalem:conditional-expectation-joint-continuity-2026aProbabilityLet be a probability space. Let be a sequence of square-integrable random variables and a square-integrable random variable on such that the mean-square distances…Mean-Square Convergence of Sub-Sigma-Algebras
definitiondef:mean-square-convergence-sigma-algebras-2026aProbabilityLet be a probability space, let be a sequence of sub--algebras of , and let be a sub--algebra of . Definition. The sequence …- Let be a probability space and let be a sequence of sub--algebras of indexed by the natural numbers that is nondecreasing: for every . Let…
The Compensated Poisson Process is a Square-Integrable Martingale
theoremthm:compensated-poisson-martingale-2026aProbabilityLet be an intensity function with mean function in the sense of Stochastic Process, Independent Increments, and Inhomogeneous Poisson Process, where is the set of real numbers, and let be an…- Let be a probability space, let be real, and let be a random variable with the Poisson distribution with parameter . Then is square-integrable and, with the expectation and variance of the cited definition,…
Square-Integrable Martingale, Submartingale, and Supermartingale
definitiondef:square-integrable-martingale-2026aProbabilityLet be a filtered probability space and let be a stochastic process on . Write for the function equal to on and off . The process is a…Basic Properties of Conditional Expectation for Square-Integrable Random Variables
lemmalem:conditional-expectation-properties-2026aProbabilityLet be a probability space, let be a sub--algebra of , and let be square-integrable random variables on it. Let be a conditional expectation of given and a conditional expectation of…Conditional Expectation of a Square-Integrable Random Variable
definitiondef:conditional-expectation-l2-2026aProbabilityLet be a probability space, let be a sub--algebra of , and let be a square-integrable random variable on it. Write for the function equal to on and off . Definition. A random variable…Existence and Uniqueness of Conditional Expectation for Square-Integrable Random Variables
theoremthm:conditional-expectation-l2-2026aProbabilityLet be a probability space, let be a sub--algebra of , and let be a square-integrable random variable on it. Call a random variable -measurable if for every Borel set , a…Mean-Square Completeness of Square-Integrable Random Variables (Riesz-Fischer)
lemmalem:mean-square-completeness-2026aProbabilityLet be a probability space, let be a sub--algebra of , and let be a sequence of square-integrable random variables on , each -measurable in the sense that…Cauchy-Schwarz and Triangle Inequalities for the Mean-Square Norm
lemmalem:cauchy-schwarz-mean-square-2026aProbabilityLet be a probability space and let and be square-integrable random variables on it, with the mean-square inner product and norm of the same definition. Then:…Square-Integrable Random Variables and the Mean-Square Inner Product
definitiondef:square-integrable-mean-square-2026aProbabilityLet be a probability space and the set of real numbers. Preliminaries. For random variables on , the functions , (), , and are again random variables: differences and sums a…Filtration, Adapted Process, and Natural Filtration
definitiondef:filtration-adapted-process-2026aProbabilityLet be a probability space and the set of real numbers. Filtration. A filtration on is a family of sub--algebras of indexed by the nonnegative real numbers such that…Thinning: Cell Counts of a Poisson Number of Independent Points
lemmalem:poisson-thinning-2026aProbabilityLet be a probability space, the set of natural numbers with , and the set of real numbers. Let be real, let be a random variable with the Poisson distribution with parameter ,…Factorized Joint Probability Mass Function Implies Independence
lemmalem:factorized-pmf-independence-2026aProbabilityLet be a probability space, let be the set of natural numbers with , and let . Let be random variables such that for every and ev…Multinomial Distribution of Cell Counts for Independent Identically Distributed Points
lemmalem:multinomial-cell-counts-2026aProbabilityLet be a probability space, let be the set of natural numbers with , and let . Let be independent random variables, each with the same distribution . Let …