Fig. 7: Power spectral densities (PSD) of numerically generated polystyrene (PS)-polymethylmethacrylate (PMMA) interfaces with different initial perturbations.

Power spectral density of h_PMMA at different times t for the numerical solutions of Fig. 6 shown for stable perturbation a and for unstable perturbations b. Corresponding PSDs normalized with respect to the PSD at t = 0 are shown in c for stable perturbation and in d for unstable perturbations. The dashed line in each panel shows the fastest-growing wavelength \({\lambda }_{\max }\) and the dash-dotted line shows the critical wavelength λ_crit from the linear stability analysis. The times in the legends of a, b are given in units of 10³ s.