On the windings of complex-valued Ornstein-Uhlenbeck processes driven by a Brownian motion and by a Stable process.
Résumé
We deal with a complex-valued Ornstein-Uhlenbeck (OU) process with parameter $\lambda\in\mathbb{R}$starting from a point different from 0 and the way that it winds around the origin.The starting point of this paper is the skew product representation for an OU process which is associated to the skew product representationof its driving planar Brownian motion under a new deterministic time scale.We present the stochastic differential equations (SDEs)for the radial and for the winding process. Moreover, we obtain the large time (analogue of Spitzer's Theorem for Brownian motion in the complex plane) and the small time asymptotics for the winding and for the radialprocess, and we explore the exit time from a cone for a 2-dimensional OU process.Some Limit Theorems concerning the angle of the cone (when our process winds in a cone) and the parameter $\lambda$ are also presented.Furthermore, we discuss the decomposition of the winding process of a complex-valued OU process in "small" and "big" windings,where, for the "big" windings, we use some results already obtained by Bertoin and Werner in \cite{BeW94},and we show that only the "small" windings contribute in the large time limit.Finally, we study the windings of a complex-valued OU process driven by a Stable processand we obtain similar results for its (well-defined) winding and radial process.
Mots clés
Complex-valued Ornstein-Uhlenbeck process
planar Brownian motion
windings
skew-product representation
exit time from a cone
Spitzer's Theorem
Stochastic Differential Equations
Bougerol's identity in law
Limit Theorems
radial and angular process
big and small windings
Lévy processes
Stable processes
isotropic Markov processes
subordination
Ornstein-Uhlenbeck processes driven by a Lévy process
Domaines
Probabilités [math.PR]
Origine : Fichiers produits par l'(les) auteur(s)
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