Figure 1

(Color online) Frequency of cooperators, $f_c$, as a function of the temptation to defect, $b$, in the scale-free networks with different assortative coefficients $r_k=0.0,0.1,0.2,0.3$, respectively. The networks have 5000 vertices and 4 connections per vertex. Each datum is averaged over 10 different networks with 10 runs for each network.Reuse & Permissions

Figure 2

(Color online) Cooperation frequency of hubs’ neighbors as a function of generation when the assortative coefficients $r_k$ of a group of scale-free networks vary from 0.0 to 0.3. The network have 5000 vertices and average degree of $⟨k⟩=4$. Initially only the maximum degree vertex is the defector and others are cooperators. The temptation to defect $b=1.5$. Evolution of cooperators around (a) the largest-degree defector with 149 connections and (b) the second largest-degree cooperator with 147 neighbors are plotted. As $r_k$ increases from 0.0 to 0.3, the two hubs share 12, 25, 43, 65 neighbors, respectively.Reuse & Permissions

Figure 3

Illustration of a subgraph, in which two connected central vertices have the same neighbors.Reuse & Permissions

Figure 4

Distribution of stationary strategies in a scale-free network with (a) $r_k=0.0$, (b) $r_k=0.3$, and $b=1.5$. Cooperators (C) and defectors (D) are denoted by gray bars and black bars, respectively. Each bar adds up to a total fraction of 1 per degree, and the gray and black fractions are directly proportional to the relative percentage of the respective strategy for each degree $k$. The data is obtained by averaging 10 runs on a network with 1000 vertices and 4 connections per vertex so that the figures can be seen clearly.Reuse & Permissions

Figure 5

(Color online) Frequency of cooperators, $f_c$, as a function of $b$ in the scale-free networks with $r_k=-0.3,-0.2,-0.1,0.0$, respectively. Other network parameters are the same as in Fig. 3.Reuse & Permissions

Figure 6

Distribution of strategies in a disassortative network with $r_k=-0.3$. (a) Initial strategies distribution and (b) stationary strategies distribution for $b=1.5$, where the strategies distribution of hubs at the end time are unchanged comparing with the initial case. Other network parameters are same as in Fig. 4.Reuse & Permissions

Figure 7

(Color online) Average degree of defectors as a function of the fraction of defectors in the scale-free networks with different mixing patterns. Networks parameters are the same as those in Figs. 3, 6.Reuse & Permissions