Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
- 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 …- Let be a probability space, let be the set of natural numbers, let be nonempty, and let be an independent family of random variables on it (for this is an independent sequence). Let b…
Sigma-Algebra Generated by Random Variables and Independence of Sigma-Algebras
definitiondef:independence-sigma-algebras-2026aProbabilityLet be a probability space, let be the set of real numbers, and let be the Borel -algebra. Generated -algebra of a family of random variables. Let be a nonempty set and let be a…- Let be a homogeneous Poisson process with rate on a probability space , so that the mean function of is for all , and let be an intensity function with mean function…
Kolmogorov Forward Equations for the Inhomogeneous Poisson Process
theoremthm:kolmogorov-forward-poisson-2026bProbabilityLet be an intensity function with mean function , and let be an inhomogeneous Poisson process with intensity on a probability space . Here denotes the set of natural numbers,…Existence of the Inhomogeneous Poisson Process
theoremthm:existence-inhomogeneous-poisson-2026bProbabilityLet be an intensity function in the sense of Stochastic Process, Independent Increments, and Inhomogeneous Poisson Process, where is the set of real numbers. Then there exist a probability space and an…Stochastic Process, Independent Increments, and Inhomogeneous Poisson Process
definitiondef:inhomogeneous-poisson-process-2026bProbabilityLet be a probability space and the set of real numbers. A stochastic process on is a family of random variables on indexed by the nonnegative real numbers. The process has…- Let be the set of natural numbers and write for the set of nonnegative integers; let be the set of real numbers and the Borel -algebra. We use the factorial for , e…
Moments and Stability of the Standard Normal Distribution
lemmalem:gaussian-stability-2026aProbabilityLet be the set of real numbers and the set of natural numbers. Claim 1. Let be a standard normal random variable on a probability space. Then , , and are integrable, and the expectation and variance satisfy…