Mason Porter

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  Migration of Populations via Marriages in the Past
  Mason Porter

  The study of human mobility is both of fundamental importance and of great potential value. For example, it can be leveraged to facilitate efficient city planning and improve prevention strategies when faced with epidemics. The wealth of rich sources of data --- including banknote flows, mobile phone records, and transportation data --- has led to an explosion of attempts to characterize modern human mobility. Unfortunately, the dearth of comparable historical data makes it much more difficult to study human mobility patterns from the past. In this talk, I present an analysis of long-term human migration, which is important for processes such as urbanization and the spread of ideas. I demonstrate that the data record from Korean family books (called "jokbo") can be used to estimate migration patterns via marriages from the past 750 years. I apply two generative models of long-term human mobility to quantify the relevance of geographical information to human marriage records in the data, and I illustrate that the wide variety in the geographical distributions of the clans poses interesting challenges for the direct application of these models. Using the different geographical distributions of clans, I quantify the ergodicity of clans in terms of how widely and uniformly they have spread across Korea, and I compare these results to those obtained using surname data from the Czech Republic. To examine population flow in more detail, I also construct and examine a population-flow network between regions. Based on the correlation between ergodicity and migration in Korea, I identify two different types of migration patterns: diffusive and convective. I expect the analysis of diffusive versus convective effects in population flows to be widely applicable to the study of mobility and migration patterns across different cultures.

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  Multilayer Networks and Applications
  Mason Porter
  One of the most active areas of network science, with an explosion of publications during the last few years, is the study of "multilayer networks," in which heterogeneous types of entities can be connected via multiple types of ties that change in time. Multilayer networks can include multiple subsystems and "layers" of connectivity, and it is important to take multilayer features into account to try to improve our understanding of complex systems. In this talk, I'll give an introduction to multilayer networks and will discuss applications in areas such as transportation, sociology, neuroscience, and ecology.
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  Topological data analysis of contagion maps for examining spreading processes on networks
  Mason Porter
  Social and biological contagions are influenced by the spatial embeddedness of networks. Historically, many epidemics spread as a wave across part of the Earth’s surface. However, in modern contagions, long-range edges --- for example, due to airline transportation or communication media --- allow clusters of a contagion to appear in distant locations. We study the spread of contagions on networks through a methodology grounded in topological data analysis and nonlinear dimension reduction. We construct "contagion maps" that use multiple contagions on a network to map the nodes as a point cloud. By analyzing the topology, geometry, and dimensionality of manifold structure in such point clouds, we reveal insights to aid in the modeling, forecast, and control of spreading processes. Our approach also highlights contagion maps as a viable tool for inferring low-dimensional structure in networks.