In most natural and engineered systems, a set of entities interact with each other in complicated patterns that can encompass multiple types of relationships, change in time, and include other types of complications Such systems include multiple subsystems and layers of connectivity, and it is important to take such "multilayer" features into account to try to improve our understanding of complex systems Consequently, it is necessary to generalize "traditional" network theory by developing (and validating) a framework and associated tools to study multilayer systems in a comprehensive fashion The origins of such efforts date back several decades and arose in multiple disciplines, and now the study of multilayer networks has become one of the most important directions in network science In this paper, we discuss the history of multilayer networks (and related concepts) and review the exploding body of work on such networks To unify the disparate terminology in the large body of recent work, we discuss a general framework for multilayer networks, construct a dictionary of terminology to relate the numerous existing concepts to each other, and provide a thorough discussion that compares, contrasts, and translates between related notions such as multilayer networks, multiplex networks, interdependent networks, networks of networks, and many others We also survey and discuss existing data sets that can be represented as multilayer networks We review attempts to generalize single-layer-network diagnostics to multilayer networks We also discuss the rapidly expanding research on multilayer-network models and notions like community structure, connected components, tensor decompositions, and various types of dynamical processes on multilayer networks We conclude with a summary and an outlook

Multilayer Networks

Tweets and the Streets analyses the culture of the new protest movements of the 21st century. From the Arab Spring to the "indignados" protests in Spain and the Occupy movement, Paolo Gerbaudo examines the relationship between the rise of social media and the emergence of new forms of protest. Gerbaudo argues that activists' use of Twitter and Facebook does not fit with the image of a "cyberspace" detached from physical reality. Instead, social media is used as part of a project of re-appropriation of public space, which involves the assembling of different groups around "occupied" places such as Cairo's Tahrir Square or New York's Zuccotti Park. An exciting and invigorating journey through the new politics of dissent, Tweets and the Streets points both to the creative possibilities and to the risks of political evanescence which new media brings to the contemporary protest experience.

http://www.tacticalmediafiles.net/mmbase/attachments/5000/Tweets__the_Streets_Introduction.pdf

Tweets and the Streets: Social Media and Contemporary Activism

How does network structure affect diffusion? Recent studies suggest that the answer depends on the type of contagion. Complex contagions, unlike infectious diseases (simple contagions), are affected by social reinforcement and homophily. Hence, the spread within highly clustered communities is enhanced, while diffusion across communities is hampered. A common hypothesis is that memes and behaviors are complex contagions. We show that, while most memes indeed spread like complex contagions, a few viral memes spread across many communities, like diseases. We demonstrate that the future popularity of a meme can be predicted by quantifying its early spreading pattern in terms of community concentration. The more communities a meme permeates, the more viral it is. We present a practical method to translate data about community structure into predictive knowledge about what information will spread widely. This connection contributes to our understanding in computational social science, social media analytics, and marketing applications.

/pdf/virality-prediction-and-community-structure-in-social-572nr9ul0a.pdf

Virality prediction and community structure in social networks

The large availability of user provided contents on online social media facilitates people aggregation around shared beliefs, interests, worldviews and narratives In spite of the enthusiastic rhetoric about the so called collective intelligence unsubstantiated rumors and conspiracy theories—eg, chemtrails, reptilians or the Illuminati—are pervasive in online social networks (OSN) In this work we study, on a sample of 12 million of individuals, how information related to very distinct narratives—ie main stream scientific and conspiracy news—are consumed and shape communities on Facebook Our results show that polarized communities emerge around distinct types of contents and usual consumers of conspiracy news result to be more focused and self-contained on their specific contents To test potential biases induced by the continued exposure to unsubstantiated rumors on users’ content selection, we conclude our analysis measuring how users respond to 4,709 troll information—ie parodistic and sarcastic imitation of conspiracy theories We find that 7792% of likes and 8086% of comments are from users usually interacting with conspiracy stories

https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0118093&type=printable

Science vs conspiracy: collective narratives in the age of misinformation.

Action to tackle the complex and divisive issue of climate change will be strongly influenced by public perception. Online social media and associated social networks are an increasingly important forum for public debate and are known to influence individual attitudes and behaviours – yet online discussions and social networks related to climate change are not well understood. Here we construct several forms of social network for users communicating about climate change on the popular microblogging platform Twitter. We classify user attitudes to climate change based on message content and find that social networks are characterised by strong attitude-based homophily and segregation into polarised “sceptic” and “activist” groups. Most users interact only with like-minded others, in communities dominated by a single view. However, we also find mixed-attitude communities in which sceptics and activists frequently interact. Messages between like-minded users typically carry positive sentiment, while messages between sceptics and activists carry negative sentiment. We identify a number of general patterns in user behaviours relating to engagement with alternative views. Users who express negative sentiment are themselves the target of negativity. Users in mixed-attitude communities are less likely to hold a strongly polarised view, but more likely to express negative sentiment towards other users with differing views. Overall, social media discussions of climate change often occur within polarising “echo chambers”, but also within “open forums”, mixed-attitude communities that reduce polarisation and stimulate debate. Our results have implications for public engagement with this important global challenge.

Network analysis reveals open forums and echo chambers in social media discussions of climate change

The number of people using online social networks in their everyday life is continuously growing at a pace never saw before. This new kind of communication has an enormous impact on opinions, cultural trends, information spreading and even in the commercial success of new products. More importantly, social online networks have revealed as a fundamental organizing mechanism in recent country-wide social movements. In this paper, we provide a quantitative analysis of the structural and dynamical patterns emerging from the activity of an online social network around the ongoing May 15th (15M) movement in Spain. Our network is made up by users that exchanged tweets in a time period of one month, which includes the birth and stabilization of the 15M movement. We characterize in depth the growth of such dynamical network and find that it is scale-free with communities at the mesoscale. We also find that its dynamics exhibits typical features of critical systems such as robustness and power-law distributions for several quantities. Remarkably, we report that the patterns characterizing the spreading dynamics are asymmetric, giving rise to a clear distinction between information sources and sinks. Our study represents a first step towards the use of data from online social media to comprehend modern societal dynamics.

David Francos

Papers

Structural and dynamical patterns on online social networks: the Spanish May 15th movement as a case study.