English

Laws of the iterated logarithm for a class of iterated processes

Probability 2009-11-09 v2

Abstract

Let X={X(t),t0}X=\{X(t), t\geq 0\} be a Brownian motion or a spectrally negative stable process of index 1<\a<21<\a<2. Let E={E(t),t0}E=\{E(t),t\geq 0\} be the hitting time of a stable subordinator of index 0<β<10<\beta<1 independent of XX. We use a connection between X(E(t))X(E(t)) and the stable subordinator of index β/\a\beta/\a to derive information on the path behavior of X(Et)X(E_t). This is an extension of the connection of iterated Brownian motion and (1/4)-stable subordinator due to Bertoin \cite{bertoin}. Using this connection, we obtain various laws of the iterated logarithm for X(E(t))X(E(t)). In particular, we establish law of the iterated logarithm for local time Brownian motion, X(L(t))X(L(t)), where XX is a Brownian motion (the case \a=2\a=2) and L(t)L(t) is the local time at zero of a stable process YY of index 1<γ21<\gamma\leq 2 independent of XX. In this case E(ρt)=L(t)E(\rho t)=L(t) with β=11/γ\beta=1-1/\gamma for some constant ρ>0\rho>0. This establishes the lower bound in the law of the iterated logarithm which we could not prove with the techniques of our paper \cite{MNX}. We also obtain exact small ball probability for X(Et)X(E_t) using ideas from \cite{aurzada}.

Keywords

Cite

@article{arxiv.0806.3126,
  title  = {Laws of the iterated logarithm for a class of iterated processes},
  author = {Erkan Nane},
  journal= {arXiv preprint arXiv:0806.3126},
  year   = {2009}
}

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13 pages