Fig. 9.

Comparison between numerical and Galerkin solutions for various parameters. $H(t-c)=1$ if $t>c$, and is zero otherwise. Initial functions used for Eqs. (70), (71) are $S\left(t\right)=1-10^{-5}\left(1+\frac{t}{1+\tau }\right),t\le 0$ and $I\left(t\right)=10^{-5}\left(1+\frac{t}{1+\tau }\right),t\le 0$. Initial conditions for Eqs. (72)–(77) are fitted by Galerkin projection (see the appendix).