A McKean optimal transportation perspective on Feynman-Kac formulae with application to data assimilation

Data assimilation is the task of combining mathematical models with observational data. From a mathematical perspective data assimilation leads to Bayesian inference problems which can be formulated in terms of Feynman-Kac formulae. In this paper we focus on the sequential nature of many data assimilation problems and their numerical implementation in form of Monte Carlo methods. We demonstrate how sequential data assimilation can be interpreted as time-dependent Markov processes, which is often referred to as the McKean approach to Feynman-Kac formulae. It is shown that the McKean approach has very natural links to coupling of random variables and optimal transportation. This link allows one to propose novel sequential Monte Carlo methods/particle filters. In combination with localization these novel algorithms have the potential of beating the curse of dimensionality, which has prevented particle filters from being applied to spatially extended systems.