On the asymptotics of extremal $$\ell ^p-$$blocks cluster inference
Gloria Buriticá, Olivier Wintenberger · Extremes · 2025
Abstract Extremes occur in stationary regularly varying time series as short periods with several large observations, known as extremal blocks. We study cluster statistics summarizing the behavior of functions acting on these extremal blocks. Examples of cluster statistics are the extremal index, cluster size probabilities, and other cluster indices. The purpose of our work is twofold. First, we state the asymptotic normality of block estimators for cluster inference based on consecutive observations with large $$\ell ^p-$$ ℓ p - norms, for $$p > 0$$ p > 0 . The case $$p=\alpha $$ p = α , where $$\alpha > 0$$ α > 0 is the tail index of the time series, has specific nice properties thus we analyze the asymptotics of block estimators when approximating $${\alpha }$$ α using the Hill estimator. Second, we verify the conditions we require on classical models such as linear models and solutions of stochastic recurrence equations. Regarding linear models, we prove that the asymptotic variance of classical index cluster-based estimators is null as first conjectured in Hsing (Probab. Theory Related Fields 95 , 331–356 1993). We illustrate our findings on simulations.