Here, we show a double-well potential and the corresponding stationary distribution. In this figure, we plot as well the density corresponding to a surrogate distribution. This consists of a clipped mixture of two Gaussian distributions. The positive component of the Gaussian mixture covers values of x with high stationary density, but the negative component covers a high-energy region. The surrogate distribution is clipped in the sense that the density is set to 0 for values of x in which the density of the mixture is below a threshold. This defines a simple surrogate that does not have full support over the domain. The surrogate distribution is depicted in 7 (a), see section 9.6.1 for exact equations.