194 research outputs found
Kinetic models of immediate exchange
We propose a novel kinetic exchange model differing from previous ones in two
main aspects. First, the basic dynamics is modified in order to represent
economies where immediate wealth exchanges are carried out, instead of
reshufflings or uni-directional movements of wealth. Such dynamics produces
wealth distributions that describe more faithfully real data at small values of
wealth. Secondly, a general probabilistic trading criterion is introduced, so
that two economic units can decide independently whether to trade or not
depending on their profit. It is found that the type of the equilibrium wealth
distribution is the same for a large class of trading criteria formulated in a
symmetrical way with respect to the two interacting units. This establishes
unexpected links between and provides a microscopic foundations of various
kinetic exchange models in which the existence of a saving propensity is
postulated. We also study the generalized heterogeneous version of the model in
which units use different trading criteria and show that suitable sets of
diversified parameter values with a moderate level of heterogeneity can
reproduce realistic wealth distributions with a Pareto power law.Comment: 10 pages, 7 figure
Classical and quantum Brownian motion in an electromagnetic field
The dynamics of a Brownian particle in a constant magnetic field and
time-dependent electric field is studied in the limit of white noise, using a
Langevin approach for the classical problem and the path-integral
Feynman-Vernon and Caldeira-Leggett framework for the quantum problem. We study
the time evolution in configuration space of the probability distribution of an
initial pure state represented by an asymmetrical Gaussian wave function and
show that it can be described as the superposition of (a) the classical motion
of the center of mass, (b) a rotation around the mean position, and (c) a
spreading processes along the principal axes.Comment: Presented at FQMT15-Frontiers of Quantum and Mesoscopic
Thermodynamics, July 27-August 1, 2015, Prague, Czech Republi
Stability of charge inversion, Thomson problem and application to electrophoresis
We analyse charge inversion in colloidal systems at zero temperature using
stability concepts, and connect this to the classical Thomson problem of
arranging electrons on sphere. We show that for a finite microion charge, the
globally stable, lowest energy state of the complex formed by the colloid and
the oppositely charged microions is always overcharged. This effect disappears
in the continuous limit. Additionally, a layer of at least twice as many
microions as required for charge neutrality is always locally stable. In an
applied external electric field the stability of the microion cloud is reduced.
Finally, this approach is applied to a system of two colloids at low but finite
temperature
Econophysics: agent-based models
This article is the second part of a review of recent empirical and theoretical developments usually grouped under the heading Econophysics. In the first part, we reviewed the statistical properties of financial time series, the statistics exhibited in order books and discussed some studies of correlations of asset prices and returns. This second part deals with models in Econophysics from the point of view of agent-based modeling. Of the large number of multiagent- based models, we have identified three representative areas. First, using previous work originally presented in the fields of behavioral finance and market microstructure theory, econophysicists have developed agent-based models of order-driven markets that we discuss extensively here. Second, kinetic theory models designed to explain certain empirical facts concerning wealth distribution are reviewed. Third, we briefly summarize game theory models by reviewing the now classic minority game and related problems.
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