Abstract

In this paper we consider a class of time-changed Lévy processes that can be represented in the form $Y_{s}=X_{\mathcal{T}(s)}$, where $X$ is a Lévy process and $\mathcal{T}$ is a non-negative and non-decreasing stochastic process independent of $X$. The aim of this work is to infer on the Blumenthal-Getoor index of the process $X$ from low-frequency observations of the time-changed Lévy process $Y$. We propose a consistent estimator for this index, derive the minimax rates of convergence and show that these rates can not be improved in general. The performance of the estimator is illustrated by numerical examples.

Highlights

  • Nonparametric statistical inference for Levy-type processes have been attracting the attention of researchers for many years starting from the works of Rubin and Tucker (1959) and Basawa and Brockwell (2007)

  • In this paper we consider a class of time-changed Levy processes that can be represented in the form Ys = XT (s), where X is a Levy process and T is a non-negative and non-decreasing stochastic process independent of X

  • We consider a class of processes known as the time-changed Levy process

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Summary

Introduction

Nonparametric statistical inference for Levy-type processes have been attracting the attention of researchers for many years starting from the works of Rubin and Tucker (1959) and Basawa and Brockwell (2007). An important remark is that the statistical analysis of the time-changed Levy models is much more difficult than the one of Levy models This lies in the fact that the increments of Y are not any longer independent and that neither the process X nor T is directly observable (see Belomestny, 2011). The question remains open whether the behaviour of ν at 0, expressed in terms of the BG index, can be recovered It follows from the results of this work that a consistent estimation of the BG index of X is basically possible, provided the Levy process X is independent of T and has a nonzero diffusion part. The unique similarity between this paper and Belomestny and Panov (2013) is the main idea to use the asymptotic behaviour of the characteristic function of the increments of the price processes to infer on the Blumenthal-Getoor (BG) index.

Levy process X
Time change
Examples
Main idea
Estimation of the characteristic function
The case of known α
The case of unknown α
Numerical examples
Upper bounds
Lower bounds
Estimation of α
Estimation of γ when α is unknown

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