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Characteristic function of a multivariate normal law
Statement
Assume AC. If , then This transform uniquely determines the law, including singular Sigma.
Facts & Assumptions
Every linear projection has the specified scalar normal law, and the vector law exists. Multivariate normal law, including singular covariance.
A scalar normal has transform . Characteristic function of a normal law.
Under AC scalar laws with equal characteristic functions agree. Uniqueness of a law from its characteristic function.
Under AC all linear projection laws determine the Borel vector law. Cramer wold device.
Proof
Given: Assume AC. If , then This transform uniquely determines the law, including singular Sigma.
For fixed t, [F1] makes scalar normal of mean and variance . Evaluate its characteristic function from [F2] at scalar frequency one. This gives the displayed formula. If t=0 both sides are one; if the scalar law is the point mass at and the same formula applies.
Let Y have another Borel probability law with the same displayed vector transform. For every u and scalar s, . Scalar uniqueness [F3] identifies each pair of projection laws. Then [F4] identifies the vector laws. Thus the construction in [F1] is independent of any realization choices. No determinant or inverse of Sigma is used. AC is inherited from [F1]–[F4]; in dimension zero the single possible law makes the assertion immediate.
Depends on
Used by
- Matching minimax rate in a Gaussian orthogonal sequence model Corollary
- Vector Levy characterization Corollary
- Two visits can alias random-slope and residual variance components Counterexample
- Canonical group-sequential alpha-spending design Definition
- Chi-square laws, including zero degrees Definition
- d-dimensional Brownian motion Definition
- The iid multivariate-normal sample and covariance conventions Definition
- Wishart law by Gaussian outer products Definition
- A degenerate multivariate Gaussian limit Example
- A hidden common cause is observationally indistinguishable from an edge Example
- An iid Gaussian cylinder process is not an ℓ²-valued prior Example
- Covariance of deterministic Ito integrals Example
- A deterministic Itô integral has independent Gaussian increments Lemma
- A finite stack of independent Gaussian vectors is jointly Gaussian Lemma
- A Gaussian error contrast has the induced multivariate-normal law Lemma
- Adjacent iid vector functionals admit a finite-moment strong approximation Lemma
- Bounded independent vector rows admit a logarithmic cubed Gaussian coupling Lemma
- Brownian covariance is equivalent to independent stationary normal increments Lemma
- Consistency of Brownian finite-dimensional laws Lemma
- Continuity of bivariate Gaussian feature expectations, including singular limits Lemma
- Endpoint law and restriction density of a scalar Brownian bridge Lemma
- Finite Sudakov–Fernique comparison for Gaussian maxima Lemma
- Finite-dimensional LAN convolution bound for differentiable functionals Lemma
- Gaussian anchored bounded sums have uniform cumulant and Fourier bounds Lemma
- Heterogeneous bounded atom vector rows admit a logarithmic cubed Gaussian coupling Lemma
- Invariant Gaussian law and uniqueness for a stable autoregression Lemma
- Jointly Gaussian blocks with zero cross-covariance are independent, including singular blocks Lemma
- Mean and covariance determine Gaussian finite-dimensional laws Lemma
- Moderate deviation density bounds for Gaussian anchored sums Lemma
- The pCN Gaussian reference pair law is symmetric Lemma
- Uncorrelated jointly Gaussian Banach random elements are independent Lemma
- Uncorrelated jointly Gaussian blocks are independent Lemma
- The limiting neural tangent kernel is strictly positive definite on every unit sphere Proposition
- Computational costs and limits of finite Gaussian-process regression Remark
- A mean and positive-semidefinite kernel define a Gaussian process Theorem
- A positive-definite multivariate normal law has its Gaussian density Theorem
- Borell concentration for the norm of a separable Banach Gaussian Theorem
- Cameron–Martin translation formula for a separable Banach Gaussian Theorem
- Convolution bound for regular estimators Theorem
- Exact increment laws in the dyadic Brownian bridge tree Theorem
…and 13 more results.
Dependency tree · two levels
51 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- Norris, Probability and Measure, Theorem 8.2.1 (standard reference, not scraped)
- Aldous and Chewi, Probability Theory notes, Theorem 8.2 (standard reference, not scraped)