## Bernoulli

• Bernoulli
• Volume 14, Number 1 (2008), 91-124.

### Multiple integral representation for functionals of Dirichlet processes

Giovanni Peccati

#### Abstract

We point out that a proper use of the Hoeffding–ANOVA decomposition for symmetric statistics of finite urn sequences, previously introduced by the author, yields a decomposition of the space of square-integrable functionals of a Dirichlet–Ferguson process, written $L^2(D)$, into orthogonal subspaces of multiple integrals of increasing order. This gives an isomorphism between $L^2(D)$ and an appropriate Fock space over a class of deterministic functions. By means of a well-known result due to Blackwell and MacQueen, we show that each element of the $n$th orthogonal space of multiple integrals can be represented as the $L^2$ limit of $U$-statistics with degenerate kernel of degree $n$. General formulae for the decomposition of a given functional are provided in terms of linear combinations of conditioned expectations whose coefficients are explicitly computed. We show that, in simple cases, multiple integrals have a natural representation in terms of Jacobi polynomials. Several connections are established, in particular with Bayesian decision problems, and with some classic formulae concerning the transition densities of multiallele diffusion models, due to Littler and Fackerell, and Griffiths. Our results may also be used to calculate the best approximation of elements of $L^2(D)$ by means of $U$-statistics of finite vectors of exchangeable observations.

#### Article information

Source
Bernoulli, Volume 14, Number 1 (2008), 91-124.

Dates
First available in Project Euclid: 8 February 2008

https://projecteuclid.org/euclid.bj/1202492786

Digital Object Identifier
doi:10.3150/07-BEJ5169

Mathematical Reviews number (MathSciNet)
MR2401655

Zentralblatt MATH identifier
1175.60072

#### Citation

Peccati, Giovanni. Multiple integral representation for functionals of Dirichlet processes. Bernoulli 14 (2008), no. 1, 91--124. doi:10.3150/07-BEJ5169. https://projecteuclid.org/euclid.bj/1202492786

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