Simón Bolívar University

About: Simón Bolívar University is a education organization based out in Caracas, Venezuela. It is known for research contribution in the topics: Population & Crystallization. The organization has 5912 authors who have published 8294 publications receiving 126152 citations.

The noisy Hegselmann-Krause model for opinion dynamics

Abstract: In the model for continuous opinion dynamics introduced by Hegselmann and Krause, each individual moves to the average opinion of all individuals within an area of confidence. In this work we study the effects of noise in this system. With certain probability, individuals are given the opportunity to change spontaneously their opinion to another one selected randomly inside the opinion space with different rules. If the random jump does not occur, individuals interact through the Hegselmann-Krause’s rule. We analyze two cases, one where individuals can carry out opinion random jumps inside the whole opinion space, and other where they are allowed to perform jumps just inside a small interval centered around the current opinion. We found that these opinion random jumps change the model behavior inducing interesting phenomena. Using pattern formation techniques, we obtain approximate analytical results for critical conditions of opinion cluster formation. Finally, we compare the results of this work with the noisy version of the Deffuant et al. model [G. Deffuant, D. Neu, F. Amblard, G. Weisbuch, Adv. Compl. Syst. 3, 87 (2000)] for continuous-opinion dynamics.

Arguing for decisions: a qualitative model of decision making

Abstract: We develop a qualitative model of decision making with two aims: to describe how people make simple decisions and to enable computer programs to do the same. Current approaches based on Planning or Decision Theory either ignore uncertainty and tradeoffs, or provide languages and algorithms that are too complex for this task. The proposed model provides a language based on rules, a semantics based on high probabilities and lexicographical preferences, and a transparent decision procedure where reasons for and against decisions interact. The model is no substitute for Decision Theory, yet for decisions that people find easy to explain it may provide an appealing alternative.

Global Observational Needs and Resources for Marine Biodiversity

Abstract: Living resources in the sea are essential to the economic, nutritional, recreational, and health needs of billions of people. Variation in the biodiversity that characterizes marine systems, and which underlies numerous ecosystem services provided to humans, is being rapidly altered by changing environmental factors and human activity. Understanding the underlying causes of these patterns, and forecasting where future changes are likely to occur, requires monitoring of patterns of organism abundance, diversity, distribution and health; productivity and ecosystem function; and allelic diversity and genetic expression. To achieve this goal it is necessary that these observations are accompanied by metrics of environmental and socio-economic drivers. However, existing global ocean observing activities often do not explicitly consider observations of marine biodiversity and associated processes. Implementing operational programs to observe life in the sea is increasingly critical to understanding responses of species and ecosystems to stressors, and overall impacts on critical natural capital, ecosystem services, and human welfare. Here we describe efforts in the global community to advance broad partnerships, shared approaches and best practices toward a standardized yet flexible, integrated observing system that serves information needs of resource managers and decision-makers, scientists and educators, from local to global scales.

Kinetics of a mixed Ising ferrimagnetic system

Abstract: We present a study, within a mean-field approach, of the kinetics of a classical mixed Ising ferrimagnetic model on a square lattice, in which the two interpenetrating square sublattices have spins $\ensuremath{\sigma}=\ifmmode\pm\else\textpm\fi{}1/2$ and $S=\ifmmode\pm\else\textpm\fi{}1,0.$ The kinetics is described by a Glauber-type stochastic dynamics in the presence of a time-dependent oscillating external field and a crystal field interaction. We can identify two types of solutions: a symmetric one, where the total magnetization $M$ oscillates around zero, and an antisymmetric one where $M$ oscillates around a finite value different from zero. There are regions of the phase space where both solutions coexist. The dynamical transition from one regime to the other can be of first or second order depending on the region in the phase diagram. Depending on the value of the crystal field we found up to two dynamical tricritical points where the transition changes from continuous to discontinuous. Also, we perform a similar study on the Blume-Capel $(S=\ifmmode\pm\else\textpm\fi{}1,0)$ model and find strong differences between its behavior and the one of the mixed model.