In full generality (including the p-space and x-space drift terms, which are often neglected) the equation is represented analogously to the Boltzmann equation. [ ∂ ∂ ∂ ∂ t + v ⋅ ⋅ ∇ ∇ x + F ⋅ ⋅ ∇ ∇ p ] f ( x , p , t ) = Q [ f ] ( x , p )