## On recursive estimation for time varying autoregressive processes.(English)Zbl 1084.62089

Summary: This paper focuses on recursive estimation of time varying autoregressive processes in a nonparametric setting. The stability of the model is revisited and uniform results are provided when the time-varying autoregressive parameters belong to appropriate smoothness classes. An adequate normalization for the correction term used in the recursive estimation procedure allows for very mild assumptions on the innovations distributions. The rate of convergence of the pointwise estimates is shown to be minimax in $$\beta$$-Lipschitz classes for $$0<\beta\leq 1$$. For $$1< \beta\leq 2$$, this property no longer holds. This can be seen by using an asymptotic expansion of the estimation error. A bias reduction method is then proposed for recovering the minimax rate.

### MSC:

 62M10 Time series, auto-correlation, regression, etc. in statistics (GARCH) 62G08 Nonparametric regression and quantile regression 62G20 Asymptotic properties of nonparametric inference

### Keywords:

locally stationary processes; nonparametric estimation
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### References:

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