Multivariate Fokker-Planck probability current (source code)

= Multivariate Fokker-Planck probability current
{c}
{title2=$J_i$}

For
$$
\partial_tP=-\partial_i(A_iP)+\frac12\partial_i\partial_j(B_{ij}P),
$$
the probability current is
$$
J_i=A_iP-\frac12\partial_j(B_{ij}P),
$$
so the equation is the continuity equation $\partial_tP+\partial_iJ_i=0$.