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world:kolmogorov

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world:kolmogorov [2023/11/15 00:23]
rdouc [Forward Kolmogorov equation]
world:kolmogorov [2023/11/15 00:23] (current)
rdouc [Forward Kolmogorov equation]
Line 32: Line 32:
 \begin{align*} \begin{align*}
     \int_\rset h(y) \condtrans{t|s}{y}{x} \rmd y - h(x) &= \PE[h(X_t)|X_s]|_{X_s=x}-h(x) ​  ​\\ ​     \int_\rset h(y) \condtrans{t|s}{y}{x} \rmd y - h(x) &= \PE[h(X_t)|X_s]|_{X_s=x}-h(x) ​  ​\\ ​
-    & =\PE_x\lrb{\int_0^t h'​(X_u) \mu_u(X_u)+\frac 1 2 h''​(X_u) \sigma_u^2(X_u) \rmd u } \\ +    & =\PE_x\lrb{\int_s^t h'​(X_u) \mu_u(X_u)+\frac 1 2 h''​(X_u) \sigma_u^2(X_u) \rmd u } \\ 
     & =\int_s^t ​ \lr{\int_\rset h'(y) \mu_u(y) \condtrans{u|s}{y}{x}\rmd y +\frac 1 2 \int_\rset h''​(y) \sigma^2_u(y) \condtrans{u|s}{y}{x} \rmd y}\rmd u  \\      & =\int_s^t ​ \lr{\int_\rset h'(y) \mu_u(y) \condtrans{u|s}{y}{x}\rmd y +\frac 1 2 \int_\rset h''​(y) \sigma^2_u(y) \condtrans{u|s}{y}{x} \rmd y}\rmd u  \\ 
     & =  \int_s^t ​ \lr{-\int_\rset h(y) \partial_y \lrb{{\mu_u(y) \condtrans{u|s}{y}{x}}}\rmd y +\frac 1 2 \int_\rset h(y) \partial^2_{yy} \lrb{\sigma^2_u(y) \condtrans{u|s}{y}{x}} \rmd y}\rmd u      & =  \int_s^t ​ \lr{-\int_\rset h(y) \partial_y \lrb{{\mu_u(y) \condtrans{u|s}{y}{x}}}\rmd y +\frac 1 2 \int_\rset h(y) \partial^2_{yy} \lrb{\sigma^2_u(y) \condtrans{u|s}{y}{x}} \rmd y}\rmd u 
world/kolmogorov.1700004217.txt.gz · Last modified: 2023/11/15 00:23 by rdouc