Prohorov-type local limit theorems on abstract Wiener spaces

TL;DR

This paper establishes Prohorov-type local limit theorems on abstract Wiener spaces, showing convergence of normalized sums of i.i.d. random variables to a Gaussian density with a different covariance structure, extending previous results.

Contribution

It generalizes existing local limit theorems to infinite-dimensional Gaussian spaces without requiring covariance matching, using advanced Wiener space tools.

Findings

Convergence of densities in  to a Gaussian measure with distinct covariance.

Extension of local limit theorems to non-trivial limiting objects.

Application to dimension-independent Berry-Esseen bounds and stochastic differential equations.

Abstract

We prove that the density of $\frac{X_1+\cdot\cdot\cdot+X_n-nE[X_1]}{\sqrt{n}}$, where $\{X_n\}_{n\geq 1}$ is a sequence of independent and identically distributed random variables taking values on an abstract Wiener space, converges in $\mathcal{L}^1$ to the density of a certain Gaussian measure which is absolutely continuous with respect to the reference Wiener measure. The crucial feature in our investigation is that we do not require the covariance structure of $\{X_n\}_{n\geq 1}$ to coincide with the one of the Wiener measure. This produces a non trivial (different from the constant function one) limiting object which reflects the different covariance structures involved. The present paper generalizes the results proved in [18] and deepens the connection between local limit theorems on (infinite dimensional) Gaussian spaces and some key tools from the Analysis on the Wiener space, like the Wiener-It\^o chaos decomposition, Ornstein-Uhlenbeck semigroup and Wick product. We also verify and discuss our main assumptions on some examples arising from the applications: dimension independent Berry-Esseen-type bounds and weak solutions of stochastic differential equations.