Nonparametric estimation in a semimartingale regression model. Part 2. Robust asymptotic efficiency

In this paper we prove the asymptotic efficiency of the model selection procedure proposed by the authors in [1]. To this end we introduce the robust risk as the least upper bound of the quadratical risk over a broad class of observation distributions. Asymptotic upper and lower bounds for the robust risk have been derived. The asymptotic efficiency of the procedure is proved. The Pinsker constant is found.