Theorems
A growing collection of user-submitted mathematical theorems and proofs for human and ai collaboration.
Existence and Uniqueness of Conditional Expectations
theoremthm:conditional-expectation-l2-2026bProbabilityUnder dependent choice, for every σ-algebra G contained in F, an integrable random variable X has a G-measurable integrable Y with the same integrals as X over the sets of G; any two such Y agree almost surely, without choice; and the same holds componentwise for integrable rando…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 the set of natural numbers, write for the nonnegative integers, and let be the set of real numbers. We use the factorial for together with the conventions and for every real…
Independence of σ-Algebras: π-Systems, Grouping and Pairs
lemmalem:grouping-independent-rvs-2026bProbabilitySubfamilies of independent families are independent; independent π-systems generate independent σ-algebras; σ-algebras generated by disjoint groups of an independent family are independent; and independence of two σ-algebras agrees with independence of the two-member family.Independence of Classes of Events and of σ-Algebras
definitiondef:independence-sigma-algebras-2026bProbabilityA family of classes of events is independent if the probability of every intersection of events from finitely many distinct classes is the product of their probabilities; σ-algebras are independent if they are so as classes.- 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-2026cProbabilityLet be a probability space and let be the 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…
Agreement of the Riemann and Lebesgue Integrals for Continuous Functions on a Closed Interval
lemmalem:riemann-lebesgue-integral-agree-2026bAnalysisLet be real numbers, let be the closed interval determined by and , and let be the real line, that is, equipped with the absolute value metric. Let be continuous on , as a map from the s…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…Existence of Independent Sequences with Prescribed Distributions
theoremthm:existence-independent-sequence-2026aProbabilityLet be a sequence of probability measures on , where is the set of real numbers, is the Borel -algebra, and is the set of natural numbers. Then there exist…Joint Distribution, Expectations, and Block Independence for Independent Random Variables
theoremthm:independent-block-functions-2026aProbabilityThroughout, is a natural number with , is Euclidean space, denotes the real numbers, and the Borel -algebra. Define the -fold product Borel -algebra on iteratively…