Solving the second equation for ρ ρ 2 and inserting ρ ρ 2 ( Γ Γ , t ) into the first equation gives a closed equation for ρ ρ 1 (see Nakajima–Zwanzig equation). The latter equation finally gives an equation for p ( A ( Γ Γ ) , t ) = p 0 ( A ( Γ Γ ) ) ρ ρ 1 ( Γ Γ , t ) , where p 0 ( a ) denotes the equilibrium distribution of the slow variables.