Real instances of social systems have a bursty character, meaning that events occur in a clustered manner. For example, the figure below shows how rare events occur over time in texts (the first indicates rarer events than the second; the second, rarer than the third). This clustering phenomenon indicates how a sequence has long memory and thus exhibits self-similarity. We study methods for nonnumerical time series to quantify the degree of clustering and examine different self-similarity degrees across various systems.


  • Kumiko Tanaka-Ishii , Armin Bunde. Long-Range Memory in Literary Texts: On the Universal Clustering of the Rare Words.  PLOS One, 2016, 11.11: e0164658. [link]

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