Fig. 36.

(Color online) The contour plot shows the epidemic threshold ${\beta }_c$ as a function of $\delta z$ and $\delta \lambda$ for a two layer multiplex composed of two ER networks. The dashed line (black) is a boundary of $\partial {\beta }_c/\partial \delta \lambda >0$ for all $\delta \lambda$, and the green (blue) line indicates the lowest (highest) value of ${\beta }_c$ at a given $\delta z$. ${\beta }_c$ shows non-monotonic dependence on $\delta \lambda$.

Reprinted figure from Ref.  [247]. Courtesy of B. Min.