Hadamard fractional Brownian motion: path properties and Wiener integration

TL;DR

This paper investigates the path properties and Wiener integration of Hadamard fractional Brownian motion, a Gaussian process with unique logarithmic kernel features, extending understanding of its trajectory regularity and stochastic calculus framework.

Contribution

It provides a detailed analysis of the path properties and develops Wiener integration for Hadamard fractional Brownian motion, including the inverse representation and RKHS characterization.

Findings

Hölder continuity and quasi-helix behavior established

Power variation and local nondeterminism analyzed

Law of iterated logarithm proved

Abstract

The so-called Hadamard fractional Brownian motion, as defined in Beghin et al. (2025) by means of Hadamard fractional operators, is a Gaussian process which shares some properties with standard Brownian motion (such as the one-dimensional distribution). However, it also resembles the fractional Brownian motion in many other features as, for instance, self-similarity, long/short memory property, Wiener-integral representation. The logarithmic kernel in the Hadamard fractional Brownian motion represents a very specific and interesting aspect of this process. Our aim here is to analyze some properties of the process' trajectories (i.e. H\"{o}lder continuity, quasi-helix behavior, power variation, local nondeterminism) that are both interesting on their own and serve as a basis for the Wiener integration with respect to it. The respective integration is quite well developed, and the inverse representation is also constructed. We apply the derived ``multiplicative Sonine pairs'' to the treatment of the Reproducing Kernel Hilbert Space of the Hadamard fractional Brownian motion, and, as a result, we establish a law of iterated logarithm.