62,941 research outputs found
Degree correlations in signed social networks
We investigate degree correlations in two online social networks where users
are connected through different types of links. We find that, while subnetworks
in which links have a positive connotation, such as endorsement and trust, are
characterized by assortative mixing by degree, networks in which links have a
negative connotation, such as disapproval and distrust, are characterized by
disassortative patterns. We introduce a class of simple theoretical models to
analyze the interplay between network topology and the superimposed structure
based on the sign of links. Results uncover the conditions that underpin the
emergence of the patterns observed in the data, namely the assortativity of
positive subnetworks and the disassortativity of negative ones. We discuss the
implications of our study for the analysis of signed complex networks
Multirelational Organization of Large-scale Social Networks in an Online World
The capacity to collect fingerprints of individuals in online media has
revolutionized the way researchers explore human society. Social systems can be
seen as a non-linear superposition of a multitude of complex social networks,
where nodes represent individuals and links capture a variety of different
social relations. Much emphasis has been put on the network topology of social
interactions, however, the multi-dimensional nature of these interactions has
largely been ignored in empirical studies, mostly because of lack of data.
Here, for the first time, we analyze a complete, multi-relational, large social
network of a society consisting of the 300,000 odd players of a massive
multiplayer online game. We extract networks of six different types of
one-to-one interactions between the players. Three of them carry a positive
connotation (friendship, communication, trade), three a negative (enmity, armed
aggression, punishment). We first analyze these types of networks as separate
entities and find that negative interactions differ from positive interactions
by their lower reciprocity, weaker clustering and fatter-tail degree
distribution. We then proceed to explore how the inter-dependence of different
network types determines the organization of the social system. In particular
we study correlations and overlap between different types of links and
demonstrate the tendency of individuals to play different roles in different
networks. As a demonstration of the power of the approach we present the first
empirical large-scale verification of the long-standing structural balance
theory, by focusing on the specific multiplex network of friendship and enmity
relations.Comment: 7 pages, 5 figures, accepted for publication in PNA
Structure and evolution of a European Parliament via a network and correlation analysis
We present a study of the network of relationships among elected members of
the Finnish parliament, based on a quantitative analysis of initiative
co-signatures, and its evolution over 16 years. To understand the structure of
the parliament, we constructed a statistically validated network of members,
based on the similarity between the patterns of initiatives they signed. We
looked for communities within the network and characterized them in terms of
members' attributes, such as electoral district and party. To gain insight on
the nested structure of communities, we constructed a hierarchical tree of
members from the correlation matrix. Afterwards, we studied parliament dynamics
yearly, with a focus on correlations within and between parties, by also
distinguishing between government and opposition. Finally, we investigated the
role played by specific individuals, at a local level. In particular, whether
they act as proponents who gather consensus, or as signers. Our results provide
a quantitative background to current theories in political science. From a
methodological point of view, our network approach has proven able to highlight
both local and global features of a complex social system.Comment: 15 pages, 10 figure
Social Stability and Extended Social Balance - Quantifying the Role of Inactive Links in Social Networks
Structural balance in social network theory starts from signed networks with
active relationships (friendly or hostile) to establish a hierarchy between
four different types of triadic relationships. The lack of an active link also
provides information about the network. To exploit the information that remains
uncovered by structural balance, we introduce the inactive relationship that
accounts for both neutral and nonexistent ties between two agents. This
addition results in ten types of triads, with the advantage that the network
analysis can be done with complete networks. To each type of triadic
relationship, we assign an energy that is a measure for its average occupation
probability. Finite temperatures account for a persistent form of disorder in
the formation of the triadic relationships. We propose a Hamiltonian with three
interaction terms and a chemical potential (capturing the cost of edge
activation) as an underlying model for the triadic energy levels. Our model is
suitable for empirical analysis of political networks and allows to uncover
generative mechanisms. It is tested on an extended data set for the standings
between two classes of alliances in a massively multi-player on-line game
(MMOG) and on real-world data for the relationships between countries during
the Cold War era. We find emergent properties in the triadic relationships
between the nodes in a political network. For example, we observe a persistent
hierarchy between the ten triadic energy levels across time and networks. In
addition, the analysis reveals consistency in the extracted model parameters
and a universal data collapse of a derived combination of global properties of
the networks. We illustrate that the model has predictive power for the
transition probabilities between the different triadic states.Comment: 21 pages, 10 figure
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