Figure 6: Time evolution of mean charge amplitude, 
, in log-linear plots from solutions of Eq. (4) obtained through a finite difference integration.
, in log-linear plots from solutions of Eq. (4) obtained through a finite difference integration.From: Self-charging of identical grains in the absence of an external field
As in Fig. 2, polarizations and charges of both signs grow similarly. (a) A is fixed and A-B is varied. (b) A-B is fixed and A is varied. (c) Exponential growth rates from the slope of a fit of linear regions of log10
vs. time plots for an array of parameters. Exponents are defined as: 
, where b is a constant. Colored spots correspond to colors used in panels (a) and (b), and violet region should not grow according to stability analysis of Eq. (4).
