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Extreme inequality represents a grave challenge for impoverished individuals and poses a threat to economic growth and stability. Despite the fulfillment of affirmative action measures aimed at promoting equal opportunities, they often prove inadequate in effectively reducing inequality. Mathematical models and simulations have demonstrated that even when equal opportunities are present, wealth tends to concentrate in the hands of a privileged few, leaving the majority of the population in dire poverty. This phenomenon, known as condensation, has been shown to be an inevitable outcome in economic models that rely on fair exchange. In light of the escalating levels of inequality in the 21st century and the significant state intervention necessitated by the recent COVID-19 pandemic, an increasing number of scholars are abandoning neo-liberal ideologies. Instead, they propose a more robust role for the state in the economy, utilizing mechanisms such as taxation, regulation, and universal allocations. This paper begins with the assumption that state intervention is essential to effectively reduce inequality and to revitalize the economy. Subsequently, it conducts a comparative analysis of various taxation and redistribution mechanisms, with a particular emphasis on their impact on inequality indices, including the Gini coefficient. Specifically, it compares the effects of fortune and consumption-based taxation, as well as universal redistribution mechanisms or targeted redistribution mechanisms aimed at assisting the most economically disadvantaged individuals. The results suggest that fortune taxation are more effective than consumption-based taxation to reduce inequality.

We study a simple traffic model with a non-signalized road intersection. In this model the car arriving from the right has precedence. The vehicle dynamics far from the crossing are governed by the rules introduced by Nagel and Paczuski, which define how drivers behave when braking or accelerating. We measure the average velocity of the ensemble of cars and its flow as a function of the density of cars on the roadway. An additional set of rules is defined to describe the dynamics at the intersection assuming a fraction of drivers that do not obey the rule of precedence. This problem is treated within a game-theory framework, where the drivers that obey the rule are cooperators and those who ignore it are defectors. We study the consequences of these behaviors as a function of the fraction of cooperators and defectors. The results show that cooperation is the best strategy because it maximizes the flow of vehicles and minimizes the number of accidents. A rather paradoxical effect is observed: for any percentage of defectors the number of accidents is larger when the density of cars is low because of the higher average velocity.

In addressing the complexity inherent in comparing socioeconomic indicators across diverse countries, a substantial barrier arises from the wide array of distinct calculation approaches. Consequently, a highly pertinent question emerges: how does one compare values when the underlying calculation methodologies are diverse? In this context, we propose a multidisciplinary and heterogeneous approach, employing numerical and visual comparisons to analyze socioeconomic indicators of municipalities in the US, Brazil and other Latin American countries. We identify independent-scale patterns in three stages: initially, by compiling a database sourced from respected institutions in each country and identifying correlations within this dataset; next, by creating graphical representations using a binning methodology for scatter plots of the identified patterns; finally, by transforming the dispersions from the initial stage into graphs using a variant of the Gravitational Clustering Algorithm technique from astrophysics. We find significant relationships, specifically in the logarithmic relationship between Municipal HDI and population size. In some countries, global minima were identified, suggesting the existence of a critical population density at which municipalities above this threshold exhibit a positive and significant correlation with an increase in their HDI. Graphical abstract

We present a model for network transformation mediated by confinement, as a demonstration of a simple network dynamics that has a direct connection with real world quantities. The model has the capacity of generating complex structures similar to real world networks by the use of two parameters. Starting from an Erdös-Rényi network, nodes are randomly selected to be temporarily confined. Confined nodes form new links among themselves at the same pace they lose connections with the outside nodes. As the network evolves according to the parameters of the model, a series of non trivial network characteristics emerge: the formation of stable heterogeneous degree distributions similar to those of empirical networks, an increasing clustering coefficient, and the emergence of communities outside the confined space. Different from the traditional benchmarks used to create modular networks, there is no arbitrary definition of the number of modules, nor node meta-data defining it as a member of a particular community, nor a tunable parameter directly related with expected modularity. Modules emerge as a result of the dynamics while nodes move among them as connections are rewired. The proposed algorithm has the potential to simulate community dynamics cases in situations where time stamped network data is scarce or absent.

Adoption of a new technology depends on many factors. Marketing, advertising, social interactions, and personal convictions are relevant features when deciding to adopt, or not, a new technology. Thus, it is very important to determine the relative weight of these factors when introducing a new technology. Here we discuss an agent based model to investigate the behavior of agents exposed to advertising and social contacts. Agents may follow the social pressure, or maybe contrarians, acting against the majority, to decide if they adopt or not a new technology. First, we solve analytically the model that relies on the above quoted factors. Then, we compare the theoretical results with empirical data concerning the adoption of innovations by American households during the 20th century. The analysis of the diffusion dynamics process is done either for the whole period, or by periods based on the so-called technical-economic paradigms, according to Freeman and Perez. Three different periods are considered: before 1920, from 1920 to 1970, and after 1970. We study the evolution of the model parameters for each technical-economic period. Finally, by adjusting the key parameters we are able to collapse all the data into a universal curve that describes all the adoption processes.

We study the role of international tribunals, like the International Criminal Court (ICC), as an effective way of reducing the number and/or gravity of crimes against humanity. The action of the ICC is directed against leaders that promote or tolerate these kinds of crimes, that is, political authorities, army commanders, civil leaders, etc. In order to simulate the action of the ICC we build a hierarchical society where the most important leaders have the highest connectivity and can spread their points of view, or their orders, through a chain of less but still highly connected deputy chiefs or opinion chieftains. In this way, if they practice misconduct, corruption, or any kind of discriminatory or criminal actions against individuals or groups, it would very difficult and improbable that they will be prosecuted by the courts of their own country. It is to alleviate this situation that the ICC was created. Its mission is to process and condemn crimes against humanity though a supranational organism that can act on criminal leaders in any country. In this study, the action of the ICC is simulated by removing the corrupt leader and replacing it by a \"decent\" one. However, as the action of the corrupt leader could have spread among the population by the time the ICC acts, we try to determine if a unique action of the ICC is sufficient or if further actions are required, depending on the degree of deterioration of the human rights in the hypothetical country. The results evidence the positive effect of the ICC action with a relatively low number of interventions. The effect of the ICC is also compared with the action of the local national judiciary system.

One of the most striking characteristics of modern financial systems is their complex interdependence, comprising a network of bilateral exposures in the interbank market, in which institutions with surplus liquidity can lend to those with a liquidity shortage. Empirical studies reveal that some interbank networks have features of scale-free networks. We explore the characteristics of financial contagion in networks whose distribution of links approaches a power law, using a model that defines banks' balance sheets from information on network connectivity. By varying the parameters for the creation of the network, several interbank networks are built, in which the concentration of debt and credit comes from the distribution of links. The results suggest that networks that are more connected and have a high concentration of credit are more resilient to contagion than other types of networks analyzed.

This paper analyzes factors related with the behavior of adolescents in Conflict with the Law through the study of the relationship between recidivism in youth detention centers (YDC) and their family context, social and neighborhoods context or atmosphere. More than 2,800 teenagers received a judicial order into YDC from the Juvenile Court for Children and Youth in Porto Alegre, Brazil, between 2002 and 2008. In this paper we identify a negative correlation between a good performance on the Social Vulnerability Index (SVI) calculated in 2004, by districts in Porto Alegre, that means low social vulnerability and recidivism in YDC. Therefore, the lower social vulnerability, the higher the SVI and the lower the probability of recidivism. The information used here was obtained from 138 Medical records (with handwritten templates by Social Workers) at FASE. We propose a logistic regression model to understand explore how risk factors for delinquency in family context and social context correspond with the available statistics of adolescents in detention centers. In this capital city, an important factor to explain the recidivism in delinquency is the drug use of \"marijuana-and-solvents\" and \"crack\" when compared with the category of \"denies or does not use drugs\".

Aiming to describe the wealth distribution evolution, several models consider an ensemble of interacting economic agents that exchange wealth in binary fashion. Intriguingly, models that consider an unbiased market, that gives to each agent the same chances to win in the game, are always out of equilibrium until the perfect inequality of the final state is attained. Here we present a rigorous analytical demonstration that any system driven by unbiased binary exchanges are doomed to drive the system to perfect inequality and zero mobility.

Social and economic inequality is a plague of the XXI Century. It is continuously widening, as the wealth of a relatively small group increases and, therefore, the rest of the world shares a shrinking fraction of resources. This situation has been predicted and denounced by economists and econophysicists. The latter ones have widely used models of market dynamics which consider that wealth distribution is the result of wealth exchanges among economic agents. A simple analogy relates the wealth in a society with the kinetic energy of the molecules in a gas, and the trade between agents to the energy exchange between the molecules during collisions. However, while in physical systems, thanks to the equipartition of energy, the gas eventually arrives at an equilibrium state, in many exchange models the economic system never equilibrates. Instead, it moves toward a \"condensed\" state, where one or a few agents concentrate all the wealth of the society and the rest of agents shares zero or a very small fraction of the total wealth. Here we discuss two ways of avoiding the \"condensed\" state. On one hand, we consider a regulatory policy that favors the poorest agent in the exchanges, thus increasing the probability that the wealth goes from the richest to the poorest agent. On the other hand, we study a tax system and its effects on wealth distribution. We compare the redistribution processes and conclude that complete control of the inequalities can be attained with simple regulations or interventions.