论文标题
高维重尾时间序列的最佳稀疏估计
Optimal Sparse Estimation of High Dimensional Heavy-tailed Time Series
论文作者
论文摘要
最近,由于健康,工程和社会科学的新应用,高维矢量自动回归模型(VAR)引起了很多兴趣。时间依赖的存在为被刑罚估计技术的理论带来了额外的挑战,广泛用于分析其IID对应物。但是,最近的工作(例如[Basu和Michailidis,2015,Kock和Callot,2015])已经建立了$ \ ell_1 $ - 类别的正规化估计值的最佳一致性,用于涉及涉及高维稳定的高斯流程的型号。时间依赖性支付的唯一价格是一个额外的乘法因素,等于1的独立和相同分布(IID)数据。此外,[Wong等人,2020年]将这些结果扩展到表现“ $β$混合”依赖性的重型尾部,但速率速率是亚最佳的,而额外的因素是棘手的。 本文以两个重要的方向改进了这些结果:(i)我们建立了最佳的一致性率和相应的有限样本界限,以匹配IID数据的基础模型参数,Modulo的时间依赖性价格易于解释,并且对IID数据等于1。 (ii)我们将更一般的惩罚纳入估计中(与$ \ ell_1 $规范不同)以诱导一般的稀疏模式。采用的关键技术工具是一种针对重型尾部线性过程的新颖,易于使用的浓度,不依赖于“混合”概念并给出更严格的范围。
Recently, high dimensional vector auto-regressive models (VAR), have attracted a lot of interest, due to novel applications in the health, engineering and social sciences. The presence of temporal dependence poses additional challenges to the theory of penalized estimation techniques widely used in the analysis of their iid counterparts. However, recent work (e.g., [Basu and Michailidis, 2015, Kock and Callot, 2015]) has established optimal consistency of $\ell_1$-LASSO regularized estimates applied to models involving high dimensional stable, Gaussian processes. The only price paid for temporal dependence is an extra multiplicative factor that equals 1 for independent and identically distributed (iid) data. Further, [Wong et al., 2020] extended these results to heavy tailed VARs that exhibit "$β$-mixing" dependence, but the rates rates are sub-optimal, while the extra factor is intractable. This paper improves these results in two important directions: (i) We establish optimal consistency rates and corresponding finite sample bounds for the underlying model parameters that match those for iid data, modulo a price for temporal dependence, that is easy to interpret and equals 1 for iid data. (ii) We incorporate more general penalties in estimation (which are not decomposable unlike the $\ell_1$ norm) to induce general sparsity patterns. The key technical tool employed is a novel, easy-to-use concentration bound for heavy tailed linear processes, that do not rely on "mixing" notions and give tighter bounds.