English

How smooth can the convex hull of a L\'evy path be?

Probability 2022-07-05 v2

Abstract

We describe the rate of growth of the derivative CC' of the convex minorant of a L\'evy path at times where CC' increases continuously. Since the convex minorant is piecewise linear, CC' may exhibit such behaviour either at the vertex time τs\tau_s of finite slope s=Cτss=C'_{\tau_s} or at time 00 where the slope is -\infty. While the convex hull depends on the entire path, we show that the local fluctuations of the derivative CC' depend only on the fine structure of the small jumps of the L\'evy process and are the same for all time horizons. In the domain of attraction of a stable process, we establish sharp results essentially characterising the modulus of continuity of CC' up to sub-logarithmic factors. As a corollary we obtain novel results for the growth rate at 00 of meanders in a wide class of L\'evy processes.

Keywords

Cite

@article{arxiv.2206.09928,
  title  = {How smooth can the convex hull of a L\'evy path be?},
  author = {David Bang and Jorge González Cázares and Aleksandar Mijatović},
  journal= {arXiv preprint arXiv:2206.09928},
  year   = {2022}
}

Comments

Revised abstract, 34 pages, 3 figures, short YouTube video: https://youtu.be/9uCge3eMHQg