Excursion Theory Revisited

Martingale Functions of Brownian Motion and its Local Time


P.J. Fitzsimmons and D.M. Wroblewski




We characterize the class of local martingales of the form H(Bt , Lt) for a standard one-dimensional Brownian motion B=(Bt)t >= 0 and its local time at 0, L=(Lt)t >= 0. The main result is closely related to work of J. Oblój, who studied the local martingales of the form H(Bt , St), where St = sup0 <= s <= t Bs.

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July 12, 2007