Violent extremist group ecologies under stress

Violent extremist groups are currently making intensive use of Internet fora for recruitment to terrorism. These fora are under constant scrutiny by security agencies, private vigilante groups, and hackers, who sometimes shut them down with cybernetic attacks. However, there is a lack of experimental and formal understanding of the recruitment dynamics of online extremist fora and the effect of strategies to control them.Here, the authors utilise data on ten extremist fora that we collected for four years to develop a data-driven mathematical model that is the first attempt to measure whether (and how) these external attacks induce extremist fora to self-regulate. The results suggest that an increase in the number of groups targeted for attack causes an exponential increase in the cost of enforcement and an exponential decrease in its effectiveness. Thus, a policy to occasionally attack large groups can be very efficient for limiting violent output from these fora.Authored by Manuel Cebrian, Manuel R. Torres, Ramon Huerta and James H. Fowler

Overcoming Problems in the Measurement of Biological Complexity

In a genetic algorithm, fluctuations of the entropy of a genome over time are interpreted as fluctuations of the information that the genome's organism is storing about its environment, being this reflected in more complex organisms. The computation of this entropy presents technical problems due to the small population sizes used in practice. In this work we propose and test an alternative way of measuring the entropy variation in a population by means of algorithmic information theory, where the entropy variation between two generational steps is the Kolmogorov complexity of the first step conditioned to the second one. As an example application of this technique, we report experimental differences in entropy evolution between systems in which sexual reproduction is present or absent.Comment: 4 pages, 5 figure

Participation of Women in the Notarial Public Deed of the 16th Century. From the Constriction of the Marital Licence to the Fullness of Widowhood

This study intends to analyse the participation of the married woman and the widow in the notarial public deed of the 16th century, in Spain, in light of the notarial forms and treatises of the time and the process itself of executing a notarial public deed. Visigothic Law would gather, to certain extent, Roman limitations and the openness brought by the Christian doctrine, resulting in the different legal systems of High Medieval times, when the married woman needed a licence from her husband in order to act. Spanish Law 56 of Toro would regulate the marital licence as a general system and compulsory requirement for the valid intervention of the married woman. In the beginning of the 16th century, not a few women executed notarial deeds and wrote royal letters related to registering as residents, returning properties and shortening litigations