Bouncing skew Brownian motions
Résumé
We consider two skew Brownian motions, driven by the same Brownian motion, with different starting
points and different skewness coefficients. In [13], the evolution of the distance between the two processes,
in local time scale and up to their first hitting time is shown to satisfy a stochastic differential equation
with jumps. The jumps of this S.D.E. are naturally driven by the excursion process of one of the two skew
Brownian motions.
In this article, we show that the description of the distance of the two processes after this first hitting
time may be studied using the self similarity induced by the previous S.D.E. More precisely, we show that the
distance between the two processes in local time scale may be viewed as the unique continuous markovian
self-similar extension of the process described in [13]. This permits us to compute the law of the distance
of the two skew Brownian motions at any time in the local time scale, when both original skew Brownian
motions start from zero. As a by product, we manage to study the markovian dependence on the skewness
parameter and answer an open question formulated initially by C. Burdzy and Z.Q. Chen in [6].
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