[Quantlib-dev] question on Black-Scholes stochastic process.

[Sun, X. <xiu...@ci...>]

HI all,

In blackscholesprocess.hpp there are comment lines about what the
BlackScholesProcess stands for :

dS(t, S) = (r(t) - \frac{\sigma(t, S)^2}{2}) dt + \sigma dW_t.

For this since it is a differential format, shouldn't BS process be
dS(t, S)/S(t, S) = ... ?

Also is the drift part from the brownie motion , \frac{\sigma(t,
S)^2}{2}) , still presented in the differential format?

please help to make me clear.

Regards,
sun