ON LOCAL TIMES AND TRAJECTORIES OF THECONTINUOUS LOCAL MARTINGALES

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Zheng Weian,He Shengwu.ON LOCAL TIMES AND TRAJECTORIES OF THECONTINUOUS LOCAL MARTINGALES[J].Chinese Annals of Mathematics B,1980,1(3-4):505~510
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Authors:

Zheng Weian; He Shengwu
Abstract: Let \(M = {({M_t})_{t > 0}}\) be a continuous local martingale, then for every real a, tbere is a decomposition \[\left| {M - a} \right| = {N^{(a)}} + {L^{(a)}}\] where \({N^{(a)}}\) is a continuons local martingale and \({L^{(a)}}\) a null-initial-valued continuons predictable increasing process, i. e. local time of M at a. A point t is called a right (left) a-osoillatory point of a continuous function f defined on \({R_ + } = [0,\infty )\),if for all \(\varepsilon > 0\),\(f - a\) is a sign-ohanging function over \((t,t + s)\) \((t-s,t)\). A point t is called a two-sided a-oseillatory point of f, if t is both a right and a left a-osoiHatory point. In this paper we have shown: (1) With probability one measure \(d{L^{(a)}}(\omega )\) concentrates on the set of all two-sided a-osoillatory points of \(M.(\omega )\). (2) M is uniquely determined by its initial value \({M_0}\) and local times \({L^{(a)}},( - \infty < a < \infty )\). Furthermore M can be constructed with initial value \({M_0}\) and local times \({L^{(a)}},( - \infty < a < \infty )\). (3) Let T be a stopping time, then for almost all\(\omega \in [T < \infty ]\) either \(T(\omega )\) is a right oscillatory point of \(M.(\omega )\), or there exists \(S(\omega ) > T(\omega )\), such that \(M.(\omega )\)is constant on \((T(\omega ),S(\omega ))\).

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