1,532 research outputs found
Gamma-distribution and wealth inequality
We discuss the equivalence between kinetic wealth-exchange models, in which
agents exchange wealth during trades, and mechanical models of particles,
exchanging energy during collisions. The universality of the underlying
dynamics is shown both through a variational approach based on the minimization
of the Boltzmann entropy and a complementary microscopic analysis of the
collision dynamics of molecules in a gas. In various relevant cases the
equilibrium distribution is the same for all these models, namely a
gamma-distribution with suitably defined temperature and number of dimensions.
This in turn allows one to quantify the inequalities observed in the wealth
distributions and suggests that their origin should be traced back to very
general underlying mechanisms: for instance, it follows that the smaller the
fraction of the relevant quantity (e.g. wealth or energy) that agents can
exchange during an interaction, the closer the corresponding equilibrium
distribution is to a fair distribution.Comment: Presented to the International Workshop and Conference on:
Statistical Physics Approaches to Multi-disciplinary Problems, January 07-13,
2008, IIT Guwahati, Indi
Relaxation in statistical many-agent economy models
We review some statistical many-agent models of economic and social systems
inspired by microscopic molecular models and discuss their stochastic
interpretation. We apply these models to wealth exchange in economics and study
how the relaxation process depends on the parameters of the system, in
particular on the saving propensities that define and diversify the agent
profiles.Comment: Revised final version. 6 pages, 5 figure
Enteroaggregative Escherichia coli: An Emerging Enteric Food Borne Pathogen
Enteroaggregative Escherichia coli (EAEC) are quite heterogeneous category of an emerging enteric pathogen associated with cases of acute or persistent diarrhea worldwide in children and adults, and over the past decade has received increasing attention as a cause of watery diarrhea, which is often persistent. EAEC infection is an important cause of diarrhea in outbreak and non-outbreak settings in developing and developed countries. Recently, EAEC has been implicated in the development of irritable bowel syndrome, but this remains to be confirmed. EAEC is defined as a diarrheal pathogen based on its characteristic aggregative adherence (AA) to HEp-2 cells in culture and its biofilm formation on the intestinal mucosa with a “stacked-brick” adherence phenotype, which is related to the presence of a 60 MDa plasmid (pAA). At the molecular level, strains demonstrating the aggregative phenotype are quite heterogeneous; several virulence factors are detected by polymerase chain reaction; however, none exhibited 100% specificity. Although several studies have identified specific virulence factor(s) unique to EAEC, the mechanism by which EAEC exerts its pathogenesis is, thus, far unknown. The present review updates the current knowledge on the epidemiology, chronic complications, detection, virulence factors, and treatment of EAEC, an emerging enteric food borne pathogen
Dynamic asset trees and Black Monday
The minimum spanning tree, based on the concept of ultrametricity, is
constructed from the correlation matrix of stock returns. The dynamics of this
asset tree can be characterised by its normalised length and the mean
occupation layer, as measured from an appropriately chosen centre called the
`central node'. We show how the tree length shrinks during a stock market
crisis, Black Monday in this case, and how a strong reconfiguration takes
place, resulting in topological shrinking of the tree.Comment: 6 pages, 3 eps figues. Elsevier style. Will appear in Physica A as
part of the Bali conference proceedings, in pres
Feebly-interacting dark matter
We briefly review scenarios with feebly interacting particles (FIMPs) as dark
matter candidates. The discussion covers issues with dark matter production in
the early universe as well as signatures of FIMPs at the high energy and high
intensity frontier as well as in astroparticle and cosmology.Comment: 6 pages, 2 captioned figures. Review article for EPJ ST Special
Issue: Frontier 23: Elementary particle physics, dark matter and
astroparticle physic
UV completion of an axial, leptophobic,
The -portal is one of most popular and well-explored scenarios of dark
matter (DM). To avoid the strong constraints coming from dilepton resonance
searches at the LHC and direct detection of DM, it is usually required that in
addition to being leptophobic, the is axially coupled to either the
(fermionic) DM or the standard model (SM) quarks. The first possibility has
been extensively studied both in the context of simplified model and UV
complete scenarios. However, the studies on the second possibiliy are largely
confined to simplified models only. Here, we construct the minimal UV
completion of these models satisfying both the criteria of leptophobia and
purely axial quark coupling. The anomaly cancellation conditions demand
highly non-trivial structures, not only in the dark sector, but also in the
Higgs sector.Comment: 15 pages. Improved version with phenomenological implications
addressed and references adde
On a kinetic model for a simple market economy
In this paper, we consider a simple kinetic model of economy involving both
exchanges between agents and speculative trading. We show that the kinetic
model admits non trivial quasi-stationary states with power law tails of Pareto
type. In order to do this we consider a suitable asymptotic limit of the model
yielding a Fokker-Planck equation for the distribution of wealth among
individuals. For this equation the stationary state can be easily derived and
shows a Pareto power law tail. Numerical results confirm the previous analysis
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