Correlation between Risk Aversion and Wealth distribution

Different models of capital exchange among economic agents have been proposed recently trying to explain the emergence of Pareto's wealth power law distribution. One important factor to be considered is the existence of risk aversion. In this paper we study a model where agents posses different levels of risk aversion, going from uniform to a random distribution. In all cases the risk aversion level for a given agent is constant during the simulation. While for a uniform and constant risk aversion the system self-organizes in a distribution that goes from an unfair ``one takes all'' distribution to a Gaussian one, a random risk aversion can produce distributions going from exponential to log-normal and power-law. Besides, interesting correlations between wealth and risk aversion are found.Comment: 8 pages, 7 figures, submitted to Physica A, Proceedings of the VIII LAWNP, Salvador, Brazil, 200

Wealth redistribution with finite resources

We present a simplified model for the exploitation of finite resources by interacting agents, where each agent receives a random fraction of the available resources. An extremal dynamics ensures that the poorest agent has a chance to change its economic welfare. After a long transient, the system self-organizes into a critical state that maximizes the average performance of each participant. Our model exhibits a new kind of wealth condensation, where very few extremely rich agents are stable in time and the rest stays in the middle class.Comment: 4 pages, 3 figures, RevTeX 4 styl

The dynamics of opinion in hierarchical organizations

We study the mutual influence of authority and persuasion in the flow of opinion. Many social organizations are characterized by a hierarchical structure where the propagation of opinion is asymmetric. In the normal flow of opinion formation a high-rank agent uses its authority (or its persuasion when necessary) to impose its opinion on others. However, agents with no authority may only use the force of its persuasion to propagate their opinions. In this contribution we describe a simple model with no social mobility, where each agent belongs to a class in the hierarchy and has also a persuasion capability. The model is studied numerically for a three levels case, and analytically within a mean field approximation, with a very good agreement between the two approaches. The stratum where the dominant opinion arises from is strongly dependent on the percentage of agents in each hierarchy level, and we obtain a phase diagram identifying the relative frequency of prevailing opinions. We also find that the time evolution of the conflicting opinions polarizes after a short transient.Comment: 6 pages, 5 figures, submitted to Phys. Rev.

Transport properties of dense fluid argon

We calculate using molecular dynamics simulations the transport properties of realistically modeled fluid argon at pressures up to $\simeq 50GPa$ and temperatures up to $3000K$. In this context we provide a critique of some newer theoretical predictions for the diffusion coefficients of liquids and a discussion of the Enskog theory relevance under two different adaptations: modified Enskog theory (MET) and effective diameter Enskog theory. We also analyze a number of experimental data for the thermal conductivity of monoatomic and small diatomic dense fluids.Comment: 8 pages, 6 figure

A Problem Solving Environment for Modelling Stony Coral Morphogenesis

Apart from experimental and theoretical approaches, computer simulation is an important tool in testing hypotheses about stony coral growth. However, the construction and use of such simulation tools needs extensive computational skills and knowledge that is not available to most research biologists. Problem solving environments (PSEs) aim to provide a framework that hides implementation details and allows the user to formulate and analyse a problem in the language of the subject area. We have developed a prototypical PSE to study the morphogenesis of corals using a multi-model approach. In this paper we describe the design and implementation of this PSE, in which simulations of the coral's shape and its environment have been combined. We will discuss the relevance of our results for the future development of PSEs for studying biological growth and morphogenesis

MyriXen: Message Passing in Xen Virtual Machines over Myrinet and Ethernet

Abstract. Data access in HPC infrastructures is realized via user-level networking and OS-bypass techniques through which nodes can communicate with high bandwidth and low-latency. Virtualizing physical components requires hardware-aided software hypervisors to control I/O device access. As a result, line-rate bandwidth or lower latency message exchange over 10GbE interconnects hosted in Cloud Computing infrastructures can only be achieved by alleviating software overheads imposed by the Virtualization abstraction layers, namely the VMM and the driver domains which hold direct access to I/O devices. In this paper, we present MyriXen, a framework in which Virtual Machines efficiently share network I/O devices bypassing overheads imposed by the VMM or the driver domains. MyriXen permits VMs to optimally exchange messages with the network via a high performance NIC, leaving security and isolation issues to the Virtualization layers. Smart Myri-10G NICs provide hardware abstractions that facilitate the integration of the MX semantics in the Xen split driver model. With MyriXen, multiple VMs exchange messages using the MX message passing protocol over Myri-10G interfaces as if the NIC was assigned solely to them. We believe that MyriXen can integrate message passing based application in clusters of VMs provided by Cloud Computing infrastructures with near-native performance

Genetic Programming Applied to Mixed Integer Programming

We present the application of Genetic Programming (GP) in Branch and Bound (B&B) based Mixed Integer Linear Programming (MIP). The hybrid architecture introduced employs GP as a node selection expression generator: a GP run, embedded into the B&B process, exploits the characteristics of the particular MIP problem being solved, evolving a problem-specific node selection method. The evolved method replaces the default one for the rest of the B&B. The hybrid approach outperforms depth-first and breadth-first search, and compares well with the advanced Best Projection method

Genome-Wide linkage scan for primary open angle glaucoma: Influences of ancestry and age at diagnosis

10.1371/journal.pone.0021967PLoS ONE67e2196