Figure 1

(Color online) The degree distribution of the HK scale-free networks with different $p$. The right top inset shows the clustering coefficient $CC$ and the left bottom inset is the degree correlation coefficient $r_k$ versus $p$ on the HK scale-free network with 5000 vertices and averagely six neighbors per vertex. Each data is obtained by averaging over 100 realizations.Reuse & Permissions

Figure 2

(Color online) The frequency of cooperators, $f_C$, as a function of the multiplication factor $r$ when the probability to form triangle, $p$, increases from 0.0 to 1.0.Reuse & Permissions

Figure 3

(Color online) Two typical subgraphs: (a) the starlike-I subgraph without the triangle around hub and (b) the starlike-II subgraph with the triangle around hub. The green (light gray) ball and the red (dark gray) box denote the cooperator and the defector respectively.Reuse & Permissions

Figure 4

(Color online) (a) The frequency of cooperators $f_C$ versus the generation $t$ for scale-free networks with different clustering coefficients. Each network contains 5000 vertices and averagely each vertex has 6 neighbors. Initially there are only ten cooperators (the highest-degree vertex and its nine low-degree neighbors) and others are defectors. (b) is the fraction of cooperators per degree, $P_C\left(k\right)$, for different instants of the time evolution. The data are obtained by averaging over ten different networks with 50 runs for each network. The multiplication factor $r=1.8$.Reuse & Permissions