Celal Umut Yaran | Searcharxiv

arXiv2025

Chaotic and Predictable Representations for Markov Additive Processes with Levy Modulator

Our main result is the martingale representations for Markov additive processes where the modulator is a Levy process. These processes have three parts: the modulator, the jumps of the ordinate triggered by the modulator, and the semimartingale part of the ordinate with parameters depending on the modulator. We orthogonalize Teugels martingales constructed from these parts to give a chaotic representation of square-integrable random variables as a sum of stochastic integrals with respect to the orthogonal sequence obtained. Consequently, a predictable representation of square-integrable martingales is derived in terms of the ordinate and the Teugels martingales.

math.PR↗

arXiv2024

Long Time Behavior of General Markov Additive Processes

We study general Markov additive processes when the state space of the modulator is a Polish space. Under some regularity assumptions, our main result is the characterization of the long-time behavior of the ordinate in terms of the associated ladder time process and the excursion measure. An important application of Markov additive processes is the Lamperti-Kiu transform, which gives a correspondence between $\mathbb{R}^d\backslash \{0\}$-valued self-similar Markov processes and $S^{d-1}\times \mathbb{R}$-valued Markov additive processes. The asymptotic behavior of the radial distance from the origin of a self-similar Markov process can be characterized by the long-time behavior of the ordinate of the corresponding Markov additive process. We show the applicability of our assumptions on some well-known self-similar Markov processes.

math.PR↗