Fokker-Planck drift vector ($A_i={\sum }_r{r}_{i}W(x,r)$)

The drift vector is the expected infinitesimal displacement per unit time. For jumps $r$ with rates $W(x,r)$, it is $A_i(x)={\sum }_r{r}_{i}W(x,r)$. It is the first jump moment entering the Fokker-Planck equation.