171 research outputs found
Economic inequality and mobility in kinetic models for social sciences
Statistical evaluations of the economic mobility of a society are more
difficult than measurements of the income distribution, because they require to
follow the evolution of the individuals' income for at least one or two
generations. In micro-to-macro theoretical models of economic exchanges based
on kinetic equations, the income distribution depends only on the asymptotic
equilibrium solutions, while mobility estimates also involve the detailed
structure of the transition probabilities of the model, and are thus an
important tool for assessing its validity. Empirical data show a remarkably
general negative correlation between economic inequality and mobility, whose
explanation is still unclear. It is therefore particularly interesting to study
this correlation in analytical models. In previous work we investigated the
behavior of the Gini inequality index in kinetic models in dependence on
several parameters which define the binary interactions and the taxation and
redistribution processes: saving propensity, taxation rates gap, tax evasion
rate, welfare means-testing etc. Here, we check the correlation of mobility
with inequality by analyzing the mobility dependence from the same parameters.
According to several numerical solutions, the correlation is confirmed to be
negative.Comment: 11 pages, 6 figures. Proceedings of the Sigma-Phi Conference on
Statistical Physics, Rhodes, 201
Discretized kinetic theory on scale-free networks
The network of interpersonal connections is one of the possible heterogeneous
factors which affect the income distribution emerging from micro-to-macro
economic models. In this paper we equip our model discussed in [1,2] with a
network structure. The model is based on a system of differential equations
of the kinetic discretized-Boltzmann kind. The network structure is
incorporated in a probabilistic way, through the introduction of a link density
and of correlation coefficients , which give the
conditioned probability that an individual with links is connected to
one with links. We study the properties of the equations and give
analytical results concerning the existence, normalization and positivity of
the solutions. For a fixed network with , we investigate
numerically the dependence of the detailed and marginal equilibrium
distributions on the initial conditions and on the exponent . Our results
are compatible with those obtained from the Bouchaud-Mezard model and from
agent-based simulations, and provide additional information about the
dependence of the individual income on the level of connectivity.Comment: 17 pages, 5 figures. Proceedings of the Sigma-Phi Conference on
Statistical Physics, Rhodes, 201
The impact of different aperture distribution models and critical stress criteria on equivalent permeability in fractured rocks
From microscopic taxation and redistribution models to macroscopic income distributions
We present here a general framework, expressed by a system of nonlinear
differential equations, suitable for the modelling of taxation and
redistribution in a closed (trading market) society. This framework allows to
describe the evolution of the income distribution over the population and to
explain the emergence of collective features based on the knowledge of the
individual interactions. By making different choices of the framework
parameters, we construct different models, whose long-time behavior is then
investigated. Asymptotic stationary distributions are found, which enjoy
similar properties as those observed in empirical distributions. In particular,
they exhibit power law tails of Pareto type and their Lorenz curves and Gini
indices are consistent with some real world ones.Comment: 12 pages, 4 figures. Version submitted to Physica A on Feb 15, 201
Statistics of Correlations and Fluctuations in a Stochastic Model of Wealth Exchange
In our recently proposed stochastic version of discretized kinetic theory, the exchange of wealth in a society is modelled through a large system of Langevin equations. The deterministic part of the equations is based on non-linear transition probabilities between income classes. The noise terms can be additive, multiplicative or mixed, both with white or OrnsteinâUhlenbeck spectrum. The most important measured correlations are those between Gini inequality index G and social mobility M, between total income and G, and between M and total income. We describe numerical results concerning these correlations and a quantity which gives average stochastic deviations from the equilibrium solutions in dependence on the noise amplitude
Driving-induced crossover: from classical criticality to self-organized criticality
We propose a spin model with quenched disorder which exhibits in slow driving
two drastically different types of critical nonequilibrium steady states. One
of them corresponds to classical criticality requiring fine-tuning of the
disorder. The other is a self-organized criticality which is insensitive to
disorder. The crossover between the two types of criticality is determined by
the mode of driving. As one moves from "soft" to "hard" driving the
universality class of the critical point changes from a classical
order-disorder to a quenched Edwards-Wilkinson universality class. The model is
viewed as prototypical for a broad class of physical phenomena ranging from
magnetism to earthquakes.Comment: 4 pages, 4 figure
Testing the preservation potential of early diagenetic dolomites as geochemical archives
Early marine diagenetic dolomite is a rather thermodynamicallyâstable carbonate phase and has potential to act as an archive of marine porewater properties. However, the variety of early to late diagenetic dolomite phases that can coexist within a single sample can result in extensive complexity. Here, the archive potential of early marine dolomites exposed to extreme postâdepositional processes is tested using various types of analyses, including: petrography, fluid inclusion data, stable ÎŽ13C and ÎŽ18O isotopes, 87Sr/86Sr ratios, and UâPb age dating of various dolomite phases. In this example, a Triassic carbonate platform was dissected and overprinted (diagenetic temperatures of 50 to 430°C) in a strikeâslip zone in Southern Spain. Eight episodes of dolomitization, a dolostone cataclasite and late stage meteoric/vadose cementation were recognized. The following processes were found to be diagenetically relevant: (i) protolith deposition and fabricâpreservation, and marine dolomitization of precursor aragonite and calcite during the MiddleâLate Triassic; (ii) intermediate burial and formation of zebra saddle dolomite and precipitation of various dolomite cements in a ProtoâAtlantic opening stress regime (T ca 250°C) during the EarlyâMiddle Jurassic; (iii) dolomite cement precipitation during early Alpine tectonism, rapid burial to ca 15 km, and highâgrade anchizone overprint during Alpine tectonic evolution in the Early Eocene to Early Miocene; (iv) brecciation of dolostones to cataclasite during the onset of the Carboneras Fault Zone activity during the Middle Miocene; and (v) lateâstage regression and subsequent meteoric overprint. Data shown here document that, under favourable conditions, early diagenetic marine dolomites and their archive data may resist petrographic and geochemical resetting over time intervals of 108 or more years. Evidence for this preservation includes preserved Late Triassic seawater ÎŽ13CDIC values and primary fluid inclusion data. Data also indicate that oversimplified statements based on bulk data from other petrographicallyâcomplex dolomite archives must be considered with caution
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