Random Modulation with Spherical Symmetry

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Hauptverfasser: Bagyan, Armine, Richards, Donald
Format: Preprint
Veröffentlicht: 2025
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author Bagyan, Armine
Richards, Donald
author_facet Bagyan, Armine
Richards, Donald
contents We consider the modulation of data given by random vectors $X_n \in \mathbb{R}^{d_n}$, $n \in \mathbb{N}$. For each $X_n$, one chooses an independent modulating random vector $Ξ_n \in \mathbb{R}^{d_n}$ and forms the projection $Y_n = Ξ_n'X_n$. It is shown, under regularity conditions on $X_n$ and $Ξ_n$, that $Y_n|Ξ_n$ converges weakly in probability to a normal distribution. More broadly, the conditional joint distribution of a family of projections constructed from random samples from $X_n$ and $Ξ_n$ is shown to converge weakly to a matrix normal distribution. We derive, \textit{via} G. Pólya's characterization of the normal distribution, a necessary and sufficient condition on $Y_n$ for $Ξ_n$ to be normally distributed. When $Ξ_n$ has a spherically symmetric distribution we deduce, through I. J. Schoenberg's characterization of the spherically symmetric characteristic functions on Hilbert spaces, that the probability density function of $Y_n|Ξ_n$ converges pointwise in certain $p$th means to a mixture of normal densities and the rate of convergence is quantified, resulting in uniform convergence. The cumulative distribution function of $Y_n|Ξ_n$ is shown to converge uniformly in those $p$th means to the distribution function of the same mixture, and a Lipschitz property is obtained. Examples of distributions satisfying our results are provided; these include Bingham distributions on hyperspheres of random radii, uniform distributions on hyperspheres and hypercubes of random volumes, and multivariate normal distributions; and examples of such $Ξ_n$ include the multivariate $t$-, multivariate Laplace, and spherically symmetric stable distributions.
format Preprint
id arxiv_https___arxiv_org_abs_2510_12928
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Random Modulation with Spherical Symmetry
Bagyan, Armine
Richards, Donald
Statistics Theory
Probability
60F05, 62E20 (Primary) 62G20, 62H10 (Secondary)
We consider the modulation of data given by random vectors $X_n \in \mathbb{R}^{d_n}$, $n \in \mathbb{N}$. For each $X_n$, one chooses an independent modulating random vector $Ξ_n \in \mathbb{R}^{d_n}$ and forms the projection $Y_n = Ξ_n'X_n$. It is shown, under regularity conditions on $X_n$ and $Ξ_n$, that $Y_n|Ξ_n$ converges weakly in probability to a normal distribution. More broadly, the conditional joint distribution of a family of projections constructed from random samples from $X_n$ and $Ξ_n$ is shown to converge weakly to a matrix normal distribution. We derive, \textit{via} G. Pólya's characterization of the normal distribution, a necessary and sufficient condition on $Y_n$ for $Ξ_n$ to be normally distributed. When $Ξ_n$ has a spherically symmetric distribution we deduce, through I. J. Schoenberg's characterization of the spherically symmetric characteristic functions on Hilbert spaces, that the probability density function of $Y_n|Ξ_n$ converges pointwise in certain $p$th means to a mixture of normal densities and the rate of convergence is quantified, resulting in uniform convergence. The cumulative distribution function of $Y_n|Ξ_n$ is shown to converge uniformly in those $p$th means to the distribution function of the same mixture, and a Lipschitz property is obtained. Examples of distributions satisfying our results are provided; these include Bingham distributions on hyperspheres of random radii, uniform distributions on hyperspheres and hypercubes of random volumes, and multivariate normal distributions; and examples of such $Ξ_n$ include the multivariate $t$-, multivariate Laplace, and spherically symmetric stable distributions.
title Random Modulation with Spherical Symmetry
topic Statistics Theory
Probability
60F05, 62E20 (Primary) 62G20, 62H10 (Secondary)
url https://arxiv.org/abs/2510.12928