Asymptotically optimal estimator of the parameter of semi-linear autoregression

Abstract

The difference equations ξk = af(ξk-1) + εk, where (εk) is a square integrable difference martingale, and the differential equation dξ =-af(ξ)dt + dη, where η is a square integrable martingale, are considered. A family of estimators depending, besides the sample size n (or the observation period, if time is continuous) on some random Lipschitz functions is constructed. Asymptotic optimality of this estimators is investigated.