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In mathematics — specifically, in stochastic analysis — Dynkin's formula is a theorem giving the expected value of any suitably smooth statistic of an Itō diffusion at a stopping time. It may be seen as a stochastic generalization of the (second) fundamental theorem of calculus. It is named after the Russian mathematician Eugene Dynkin. ==Statement of the theorem== Let ''X'' be the R''n''-valued Itō diffusion solving the stochastic differential equation : For a point ''x'' ∈ R''n'', let P''x'' denote the law of ''X'' given initial datum ''X''0 = ''x'', and let E''x'' denote expectation with respect to P''x''. Let ''A'' be the infinitesimal generator of ''X'', defined by its action on compactly-supported ''C''2 (twice differentiable with continuous second derivative) functions ''f'' : R''n'' → R as : or, equivalently, : Let ''τ'' be a stopping time with E''x''() < +∞, and let ''f'' be ''C''2 with compact support. Then Dynkin's formula holds: : In fact, if ''τ'' is the first exit time for a bounded set ''B'' ⊂ R''n'' with E''x''() < +∞, then Dynkin's formula holds for all ''C''2 functions ''f'', without the assumption of compact support. 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「Dynkin's formula」の詳細全文を読む スポンサード リンク
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