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Tightly knit: spreading processes in empirical temporal networks
Umeå University, Faculty of Science and Technology, Department of Physics.
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

We live in a tightly knit world. Our emotions, desires, perceptions and decisions are interlinked in our interactions with others. We are constantly influencing our surroundings and being influenced by others. In this thesis, we unfold some aspects of social and economical interactions by studying empirical datasets. We project these interactions into a network representation to gain insights on how socio-economic systems form and function and how they change over time. Specifically, this thesis is centered on four main questions: How do the means of communication shape our social network structures? How can we uncover the underlying network of interests from massive observational data? How does a crisis spread in a real financial network? How do the dynamics of interaction influence spreading processes in networks? We use a variety of methods from physics, psychology, sociology, and economics as well as computational, mathematical and statistical analysis to address these questions.

Place, publisher, year, edition, pages
Umeå: Umeå University , 2015. , 55 p.
National Category
Natural Sciences
Research subject
Physics
Identifiers
URN: urn:nbn:se:umu:diva-98885ISBN: 978-91-7601-209-3 (print)OAI: oai:DiVA.org:umu-98885DiVA: diva2:783857
Public defence
2015-02-20, NC 300, Naturvetarhuset, Umeå, 12:00 (English)
Opponent
Supervisors
Available from: 2015-01-30 Created: 2015-01-27 Last updated: 2015-02-05Bibliographically approved
List of papers
1. Structural differences between open and direct communication in an online community
Open this publication in new window or tab >>Structural differences between open and direct communication in an online community
2014 (English)In: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 414, no 15 November, 263-273 p.Article in journal (Refereed) Published
Abstract [en]

Most research of online communication focuses on modes of communication that are either open (like forums, bulletin boards, Twitter, etc.) or direct (like e-mails). In this work, we study a dataset that has both types of communication channels. We relate our findings to theories of social organization and human dynamics. The data comprises 36,492 users of a movie discussion community. Our results show that there are differences in the way users communicate in the two channels that are reflected in the shape of degree- and interevent time distributions. The open communication that is designed to facilitate conversations with any member shows a broader degree distribution and more of the triangles in the network are primarily formed in this mode of communication. The direct channel is presumably preferred by closer communication and the response time in dialogs is shorter. On a more coarse-grained level, there are common patterns in the two networks. The differences and overlaps between communication networks, thus, provide a unique window into how social and structural aspects of communication establish and evolve.

Place, publisher, year, edition, pages
Elsevier, 2014
Keyword
multiplex networks, network theory, communication motifs
National Category
Other Physics Topics Communication Systems Communication Studies
Identifiers
urn:nbn:se:umu:diva-92058 (URN)10.1016/j.physa.2014.07.037 (DOI)000342253300028 ()2-s2.0-84906254086 (Scopus ID)
Funder
Swedish Research Council, 2012-3651
Available from: 2014-08-21 Created: 2014-08-21 Last updated: 2017-12-05Bibliographically approved
2. Mapping bilateral information interests using the activity of Wikipedia editors
Open this publication in new window or tab >>Mapping bilateral information interests using the activity of Wikipedia editors
Show others...
2015 (English)In: Palgrave communications, ISSN 2055-1045, Vol. 1, 1-7 p., 15041Article in journal (Refereed) Published
Abstract [en]

We live in a global village where electronic communication has eliminated the geographical barriers of information exchange. The road is now open to worldwide convergence of information interests, shared values and understanding. Nevertheless, interests still vary between countries around the world. This raises important questions about what today’s world map of information interests actually looks like and what factors cause the barriers of information exchange between countries. To quantitatively construct a world map of information interests, we devise a scalable statistical model that identifies countries with similar information interests and measures the countries’ bilateral similarities. From the similarities we connect countries in a global network and find that countries can be mapped into 18 clusters with similar information interests. Through regression we find that language and religion best explain the strength of the bilateral ties and formation of clusters. Our findings provide a quantitative basis for further studies to better understand the complex interplay between shared interests and conflict on a global scale. The methodology can also be extended to track changes over time and capture important trends in global information exchange.

Keyword
Information, Network, Globalization, Wikipedia
National Category
Information Systems Information Studies
Research subject
Computer and Information Science
Identifiers
urn:nbn:se:umu:diva-98814 (URN)10.1057/palcomms.2015.41 (DOI)
Note

Originally published in manuscript form with the title: Local Interests in a Global World

Available from: 2015-01-27 Created: 2015-01-27 Last updated: 2016-12-16Bibliographically approved
3. Threshold model of cascades in empirical temporal networks
Open this publication in new window or tab >>Threshold model of cascades in empirical temporal networks
2013 (English)In: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 392, no 16, 3476-3483 p.Article in journal (Refereed) Published
Abstract [en]

Threshold models try to explain the consequences of social influence like the spread of fads and opinions. Along with models of epidemics, they constitute a major theoretical framework of social spreading processes. In threshold models on static networks, an individual changes her state if a certain fraction of her neighbors has done the same. When there are strong correlations in the temporal aspects of contact patterns, it is useful to represent the system as a temporal network. In such a system, not only contacts but also the time of the contacts are represented explicitly. In many cases, bursty temporal patterns slow down disease spreading. However, as we will see, this is not a universal truth for threshold models. In this work we propose an extension of Watts’s classic threshold model to temporal networks. We do this by assuming that an agent is influenced by contacts which lie a certain time into the past. I.e., the individuals are affected by contacts within a time window. In addition to thresholds in the fraction of contacts, we also investigate the number of contacts within the time window as a basis for influence. To elucidate the model’s behavior, we run the model on real and randomized empirical contact datasets.

National Category
Other Physics Topics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-71153 (URN)10.1016/j.physa.2013.03.050 (DOI)000320292500020 ()
Funder
Swedish Research Council, 2012-3651
Available from: 2013-05-21 Created: 2013-05-21 Last updated: 2017-12-06Bibliographically approved
4. Cascades in real interbank markets
Open this publication in new window or tab >>Cascades in real interbank markets
2016 (English)In: Computational Economics, ISSN 0927-7099, E-ISSN 1572-9974, Vol. 47, no 1, 46-66 p.Article in journal (Refereed) Published
Abstract [en]

We analyze cascades of defaults in an interbank loan market. The novel feature of this study is that the network structure and the size distribution of banks are derived from empirical data. We find that the ability of a defaulted institution to start a cascade depends on an interplay of shock size and connectivity. Further results indicate that the interbank loan network is structurally less stable after the financial crisis than it was before. To evaluate the influence of the network structure on market stability, we compare simulated cascades from the empirical network with results from different network models. The results show that the empirical network has non-random features, which cannot be captured by randomized networks. The analysis also reveals that simulations that assume homogeneity for banks and loan size tend to overestimate the fragility of the interbank market.

Keyword
default cascade, interbank markets, interbank loan network, systemic risk, cascades, null models
National Category
Economics
Research subject
Economics; Physics
Identifiers
urn:nbn:se:umu:diva-96663 (URN)10.1007/s10614-014-9478-z (DOI)000367852700004 ()
Funder
Swedish Research Council
Note

2016-05-16: Originally published in manuscript form.

Available from: 2014-11-24 Created: 2014-11-24 Last updated: 2017-12-05Bibliographically approved

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