Section: New Results
Fine regularity of Lévy processes
Participant : Paul Balança.
This ongoing work focuses on the fine regularity of one-parameter Lévy processes. The main idea of this study is to use the framework of stochastic 2-microlocal analysis (introduced and developed in [16] ,[33] ) to refine sample paths results obtained in [65] .
The latter describes entirely the multifractal spectrum of Lévy processes, i.e. the Hausdorff geometry of level sets
The multifractal spectrum is itself defined as the localized Hausdorff dimension of the previous sets, i.e.
[65] states that under a mild assumption on the Lévy measure
where the Blumenthal-Getoor exponent
Since classic multifractal analysis focuses on the pointwise exponent, it is natural from our point of view to integrate the 2-microlocal frontier into this description. More precisely, we focus on the dichotomy usual/unusual regularity, corresponding to the sets
The collection
Then, our main result states that sample paths of a Lévy process
Furthermore, the collection of sets
These results clearly extend those obtained in [65] since we know that the pointwise exponent is completely characterize by the 2-microlocal frontier. Moreover, it also proves that from a Hausdorff dimension point of view, the common regularity is a 2-microlocal frontier with a slope equal to one.
Nevertheless, equation (15 ) also exhibits some unusual behaviours, corresponding to times