How Can Social Networks Ever Become Complex? Modelling the Emergence of Complex Networks from Local Social Exchanges

Small-world and power-law network structures have been prominently proposed as models of large networks. However, the assumptions of these models usually lack sociological grounding. We present a computational model grounded in social exchange theory. Agents search attractive exchange partners in a diverse population. Agent use simple decision heuristics, based on imperfect, local information. Computer simulations show that the topological structure of the emergent social network depends heavily upon two sets of conditions, harshness of the exchange game and learning capacities of the agents. Further analysis show that a combination of these conditions affects whether star-like, small-world or power-law structures emerge.Complex Networks, Power-Law, Scale-Free, Small-World, Agent-Based Modeling, Social Exchange Theory, Structural Emergence

Local Search in Unstructured Networks

We review a number of message-passing algorithms that can be used to search through power-law networks. Most of these algorithms are meant to be improvements for peer-to-peer file sharing systems, and some may also shed some light on how unstructured social networks with certain topologies might function relatively efficiently with local information. Like the networks that they are designed for, these algorithms are completely decentralized, and they exploit the power-law link distribution in the node degree. We demonstrate that some of these search algorithms can work well on real Gnutella networks, scale sub-linearly with the number of nodes, and may help reduce the network search traffic that tends to cripple such networks.Comment: v2 includes minor revisions: corrections to Fig. 8's caption and references. 23 pages, 10 figures, a review of local search strategies in unstructured networks, a contribution to `Handbook of Graphs and Networks: From the Genome to the Internet', eds. S. Bornholdt and H.G. Schuster (Wiley-VCH, Berlin, 2002), to be publishe

Emergence of Global Preferential Attachment From Local Interaction

Global degree/strength based preferential attachment is widely used as an evolution mechanism of networks. But it is hard to believe that any individual can get global information and shape the network architecture based on it. In this paper, it is found that the global preferential attachment emerges from the local interaction models, including distance-dependent preferential attachment (DDPA) evolving model of weighted networks(M. Li et al, New Journal of Physics 8 (2006) 72), acquaintance network model(J. Davidsen et al, Phys. Rev. Lett. 88 (2002) 128701) and connecting nearest-neighbor(CNN) model(A. Vazquez, Phys. Rev. E 67 (2003) 056104). For DDPA model and CNN model, the attachment rate depends linearly on the degree or strength, while for acquaintance network model, the dependence follows a sublinear power law. It implies that for the evolution of social networks, local contact could be more fundamental than the presumed global preferential attachment. This is onsistent with the result observed in the evolution of empirical email networks.Comment: 9 pages, 5 figure

DREAMS REALIZED AND DREAMS DEFERRED: SOCIAL MOVEMENTS AND PUBLIC POLICY IN PITTSBURGH, 1960-1980

This dissertation analyzes the impact of civil rights, women's rights, and gay rights activists on public policy in Pittsburgh during the 1960s and 1970s. It challenges several of the interpretations which other scholars have made about the history and impact of the New Left and social movements in the United States since 1960. This study applies social network analysis to politics to explain the successes and failures these social movements had in the city in winning the reforms that they sought for their communities. As the activists grew in their political sophistication, so their political networks matured. Pittsburgh activists did not ignore the means of power that social movement scholars traditionally study, power at the polls and in the streets. But in addition to such tools, activists built a base of trust, respect, and mutual support between themselves and local politicians. By gathering and disseminating information about the problems afflicting their communities, African-Americans in the 1960s and feminists and gays in the 1970s won converts to their cause among the city's political elite. Leaders within the three movements leveraged their growing rapport with political leaders to win appointments to government commissions for community members and appropriations for programs aiding their communities. These positions brought activists further contacts and alliances with leaders at other levels of government. Using their political networks, these Pittsburgh activists in the 1970s protected and sometimes advanced their cause even in the face of federal budget cuts and growing organized opposition to school desegregation, abortion, and gay rights