We can prove this formally by computing the relaxation time of the slowest process, t 2 , which is proportional to the projection of the surrogate distribution to the corresponding eigenfunction, ψ 2 . As ψ 2 resembles the slowest process in the system, it must change sign in 0 as shown in Figure (b). Let's say that we choose ψ 2 in such a way that is negative on the left and positive on the right. Then,