We derive an approximation of a density estimator based on weakly dependent random vectors by a density estimator built from independent random vectors. We construct, on a sufficiently rich probability space, such a pairing of the random variables of both experiments that the set of observations (X-1,..., X-n) from the time series model is nearly the same as the set of observations (Y-1,..., Y-n) from the i.i.d. model. With a high probability, all sets of the form ((X-1,..., X-n)Delta(Y-1,..., Y-n))boolean AND([a(1), b(1)] x...x [a(d), b(d)]) contain no more than O(([n(1/2) Pi(b(i) - a(i))] + 1)log(n)) elements, respectively. Although this does not imply very much for parametric problems, it has important implications in nonparametric statistics. It yields a strong approximation of a kernel estimator of the stationary density by a kernel density estimator in the i.i.d. model. Moreover, it is shown that such a strong approximation is also valid for the standard bootstrap and the smoothed bootstrap. Using these results we derive simultaneous confidence bands as well as supremum-type nonparametric tests based on reasoning for the i.i.d. model.
Neumann, M. (1998). Strong approximation of density estimators from weakly dependent observations by density estimators from independent observations. Annals of Statistics, 26(5), 2014-2048. https://hdl.handle.net/2078.5/34963 (Original work published 1998)