Adaptive efficient robust sequential analysis for autoregressive big data models

In this paper we consider high dimension models based on dependent observations defined through autoregressive processes. For such models we develop an adaptive efficient estimation method via the robust sequential model selection procedures. To this end, firstly, using the Van Trees inequality, we obtain a sharp lower bound for robust risks in an explicit form given by the famous Pinsker constant. It should be noted, that for such models this constant is calculated for the first time. Then, using the weighted least square method and sharp non asymptotic oracle inequalities we provide the efficiency property in the minimax sense for the proposed estimation procedure, i.e. we establish, that the upper bound for its risk coincides with the obtained lower bound. It should be emphasized that this property is obtained without using sparse conditions and in the adaptive setting when the parameter dimension and model regularity are unknown.