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Algorithms for Kullback--Leibler Approximation of Probability Measures in Infinite Dimensions
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Algorithms for Kullback--Leibler Approximation of Probability Measures in Infinite Dimensions

Frank J. Pinski, Gideon Simpson, Andrew M. Stuart and Hendrik Weber
SIAM Journal on Scientific Computing, v 37(6), pp A2733-A2757
08 Aug 2014
url
https://resolver.caltech.edu/CaltechAUTHORS:20160715-163821138View
Accepted (AM)Open Access (License Unspecified) Open

Abstract

Mathematics Numerical Analysis Probability
In this paper we study algorithms to find a Gaussian approximation to a target measure defined on a Hilbert space of functions; the target measure itself is defined via its density with respect to a reference Gaussian measure. We employ the Kullback--Leibler divergence as a distance and find the best Gaussian approximation by minimizing this distance. It then follows that the approximate Gaussian must be equivalent to the Gaussian reference measure, defining a natural function space setting for the underlying calculus of variations problem. We introduce a computational algorithm which is well-adapted to the required minimization, seeking to find the mean as a function, and parameterizing the covariance in two different ways: through low rank perturbations of the reference covariance and through Schrödinger potential perturbations of the inverse reference covariance. Two applications are shown: to a nonlinear inverse problem in elliptic PDEs and to a conditioned diffusion process. These Gaussian approximations also serve to provide a preconditioned proposal distribution for improved preconditioned Crank--Nicolson Monte Carlo--Markov chain sampling of the target distribution. This approach is not only well-adapted to the high dimensional setting, but also behaves well with respect to small observational noise (resp., small temperatures) in the inverse problem (resp., conditioned diffusion).\ud \ud \ud \ud \ud

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Web of Science research areas
Mathematics, Applied
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