Description In recent years, the possibility to access large digital databases, as well as the development and deployment of large scale monitoring frameworks, has allowed to peer for the first time into the statistical properties of human behavior. To our surprise, the patterns of human activity have been shown to be extremely bursty, characterized by long tailed distributions, in opposition to the Poissonian behavior expected from traditional mathematical approaches. Apart from the insights that these discoveries have in the description and hypothetical predictability of human behavior, they are most relevant due to the direct connection between the patterns of human activity and the topological description of the representative social networks. Here we will discuss recent modeling efforts designed to understand and reproduce the empirical properties of social networks, as well as their effects on simple dynamical processes.

Description The Kolmogorov-Smirnov (KS) distribution appears in statistics when testing for the maximum distance between a one-dimensional empirical distribution and some proposed reference distribution. A well-known Brownian bridge construction leads to its calculation, and further identifications with e.g. Brownian excursions or Bessel processes show that this same distribution describes a surprisingly wide variety of random observables. Intriguingly, the KS distribution is also encountered in the observables of a number of models in statistical physics, such as the height of an Edwards-Wilkinson interface, or the order parameter in mean-field critical percolation. Meanwhile, the two-dimensional analogue of the KS distribution describes e.g. the steady-state height of an Edwards-Wilkinson membrane, and the order parameter of the XY model at low tempetaures. My talk will survey such examples of the KS distribution in statistical physics.

Description

- Acte de presentació del llibre Complèxica. Cervell, societat i llengua des de la transdisciplinarietat, coordinat per Àngels Massip i Bonet i Albert Bastardas i Boada (Publicacions i Edicions de la UB). - Taula rodona: «Cognició, comunicació i comportament social en els humans: quins camins per a avançar complèxicament?», a càrrec de Frederic Munné (Psicologia social, UB); Sebastià Serrano (Lingüística General i Comunicació, UB); Òscar Vilarroya (Neurociència cognitiva, UAB). Resum de l'acte: Els fenòmens produïts a l’entorn del triangle ‘llengua-comunicació-societat’ presenten trets singulars que desafien les aproximacions científiques tradicionals i també les més formalitzadores dels sistemes complexos. ¿Com seria possible concebre i definir una classe diferent d’esdeveniments, propis dels organismes i les societats humans, que no poden ser fàcilment codificats o encapsulats per un formalisme matemàtic? Per on i com cal continuar avançant per aprofundir la seva comprensió transdisciplinària?

Organizers
Grup de Complexitat, Comunicació i Sociolingüística i el Projecte Scripta, amb el suport del Centre Universitari de Sociolingüística i Comunicació (CUSC-UB)

Description

Description The motion of water masses by ocean currents is one of the main drivers of marine biological productivity. Being an inherently chaotic phenomenon, Lyapunov exponents have found important applications in characterizing and understanding this fluid transport process. In particular, local Lyapunov-exponent methods (finite-time and finite-size) have revealed to be useful to locate barriers to transport, attracting manifolds, and similar organizing structures in fluid flows. Here we review some recent applications of finite-size Lyapunov exponents (FSLEs) to characterize ocean transport and its impact on biological processes. The identification of the so-called Lagrangian coherent structures is addressed, and we also use FSLEs for the original goal they were introduced, namely quantifying the intensity of dispersion or mixing at a particular spatial scale. We will explore here the three-dimensional structure of Benguela eddies, of the Oxygen Minimum Zone in the Eastern Tropical Pacific, the relationship between mixing intensity and biological productivity in upwelling areas, and the role of Lyapunov structures as biological corridors for marine birds.