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In the stochastic calculus, Tanaka's formula states that : where ''B''''t'' is the standard Brownian motion, sgn denotes the sign function : and ''L''''t'' is its local time at 0 (the local time spent by ''B'' at 0 before time ''t'') given by the ''L''2-limit : ==Properties== Tanaka's formula is the explicit Doob–Meyer decomposition of the submartingale |''B''''t''| into the martingale part (the integral on the right-hand side), and a continuous increasing process (local time). It can also be seen as the analogue of Itō's lemma for the (nonsmooth) absolute value function , with and ; see local time for a formal explanation of the Itō term. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Tanaka's formula」の詳細全文を読む スポンサード リンク
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