Fig. 4.

Instantaneous speed of a travelling front for non-Gaussian threshold distributions. Measured front speed, extracted from a simulation of (3) (blue); theoretical value from (21) (red); and the threshold (4) (green) for a shifted exponential distribution (top) and a bump distribution (bottom) for $\kappa =3$, $h_0=0.3$ and $L=50$. Equation (9) was truncated after 32 (top) and 64 (bottom) terms per sum, respectively. Other parameter values are $\lambda =1$, $\mu =-1$, $ϵ=-0.03$ (top) and $A=\sqrt{2}$, $B=2$, $\alpha =0.5$, $ϵ=0.05$ (bottom)