arXiv subjects

Marcelo Lobato Martins

Publications and source records attributed to Marcelo Lobato Martins.

4 recordsLinked to original sources

arXiv2026

A Fokker-Planck approach to a stochastic multiplicative wealth model with taxation and redistribution

We develop a Fokker-Planck description of the dynamics of wealth distribution in a stochastic multiplicative economic growth model with taxation and redistribution, as introduced by P.M.C. de Oliveira. Extending the original formulation, our theoretical framework includes general redistribution protocols, encompassing a broad class of state-dependent transfer mechanisms. As a particular case, we investigate a two-state protocol designed to emulate conditional cash transfer programs. Analytical expressions for the stationary wealth distributions are derived, revealing how the interplay between multiplicative noise, taxation, and redistribution shapes the emergence of inequality. The theoretical results are corroborated by agent-based simulations. To quantify and compare the impact of the different protocols, we employ the Gini index as a measure of inequality. Our analysis highlights how specific nonuniform redistribution schemes can significantly mitigate wealth disparities.

cond-mat.stat-mech↗

arXiv2025

Effects of taxes, redistribution actions and fiscal evasion on wealth inequality: an agent-based model approach

In capitalist societies, only a single right can be fully exerted without constraints of any kind: the limitless accumulation of wealth. Such imperative or prime axiom is the ultimate cause of the raising waves of inequalities observed today. In this work we extended the agent-based model proposed by Castro de Oliveira arXiv:1711.06164 to study the effects of non-uniform income redistribution policies and tax evasion on the final steady-state wealth distribution of economic agents. Our simulational results strongly support that well designed policies of income redistribution and rigid control of tax planning possibilities are unavoidable instruments to promote the raise of more economically egalitarian and sustainable societies.

physics.soc-ph↗

arXiv2018

Community structures in allelopathic interaction networks: an eco-evolutionary approach

Nowadays, evidence is mounting that the race of living organisms for adaptation to the chemicals synthesized by their neighbours may drive community structures. Particularly, some bacterial infections and plant invasions disruptive of the native community rely on the release of allelochemicals that inhibit or kill sensitive strains or individuals from their own or other species. In this report, an eco-evolutionary model for community assembly through resource competition, allelophatic interactions, and evolutionary branching is presented and studied by numerical analysis. Our major findings are that stable communities with increasing biodiversity can emerge at weak allelopathic suppression, but stronger allelophaty is negatively correlated with community diversity. In the former regime the allelopathic interaction networks exhibit Gaussian degree distributions, while in the later one the network degrees are Weibull distributed.

q-bio.PE↗

arXiv2001

Roughness exponent in two-dimensional percolation, Potts and clock models

We present a numerical study of the self-affine profiles obtained from configurations of the q-state Potts (with q=2,3 and 7) and p=10 clock models as well as from the occupation states for site-percolation on the square lattice. The first and second order static phase transitions of the Potts model are located by a sharp change in the value of the roughness exponent $α$ characterizing those profiles. The low temperature phase of the Potts model corresponds to flat ($α\simeq 1$) profiles, whereas its high temperature phase is associated to rough ($α\simeq 0.5$) ones. For the p=10 clock model, in addition to the flat (ferromagnetic) and rough (paramagnetic) profiles, an intermediate rough ($0.5< α<1$) phase - associated to a soft spin-wave one - is observed. Our results for the transition temperatures in the Potts and clock models are in agreement with the static values, showing that this approach is able to detect the phase transitions in these models directly from the spin configurations, without any reference to thermodynamical potentials, order parameters or response functions. Finally, we show that the roughness exponent $α$ is insensitive to geometric critical phenomena.

cond-mat.stat-mech↗