arXiv subjects

Eduardo V. Stock

Publications and source records attributed to Eduardo V. Stock.

8 recordsLinked to original sources

arXiv2026

Patterns in a Warming Ocean: Stylized Spectral Facts on Sea Surface Temperature

Capturing stylized facts and their evolution is essential for understanding the impact of climate change on complex environmental systems. In this work, we investigate the spectral properties of correlation matrices constructed from sea surface temperature data, employing tools from random matrix theory to identify signatures of global warming and long-term climate variability. By constructing yearly ensembles of correlation matrices, we analyze the evolution of both the eigenvalue density and the statistical behavior of the largest eigenvalue. Our results reveal significant departures from the universal behavior expected for random correlations. In particular, the empirical spectra systematically deviate from the Marchenko--Pastur law, indicating the presence of strong collective correlations in ocean temperature dynamics. Moreover, we find that the average largest eigenvalue exhibits a pronounced increase over time, closely following the rise in global mean ocean temperature. The distribution of the largest eigenvalue is found to be approximately Gaussian rather than Tracy--Widom, suggesting that the system lies outside the standard universal regime associated with weakly correlated Wishart ensembles. Together with conventional statistical indicators, these spectral signatures consistently reflect the progressive modification of the ocean-temperature correlation structure. Our findings demonstrate that spectral observables derived from correlation matrices, particularly the largest eigenvalue and its fluctuations, provide a sensitive framework for characterizing climate dynamics and detecting emerging signatures of long-term climate change.

physics.soc-ph↗

arXiv2024

Interplay of Reward and Size of Groups in the Optional Public Goods Game

The Optional Public Goods Game is a three-strategy game in which an individual can play as a cooperator or defector or decide not to participate. Despite its simplicity, this model can effectively represent many human social dilemmas, such as those found in the use of public services, environmental concerns, or other activities related to society. In this contribution, we present a comprehensive analysis of the conditions under which spontaneous, sustained cooperation emerges and the characteristics of these cooperative states. Through simulations, we demonstrate the conditions leading to the coexistence of the three strategies in a steady equilibrium or the alternate dominance of each strategy in a rock-paper-scissors fashion. The results identify each of the possible scenarios in terms of two key parameters: the multiplication rate of the public good game (reward) and the size of the group of potential players. We also discuss other details of the game that may influence the appearance of cycles, along with relevant characteristics of these cycles, such as the prevalence of cooperation.

physics.soc-ph↗

arXiv2024

Nightclub bar dynamics: statistics of serving times

In this work, we investigate the statistical properties of drink serving in a nightclub bar, utilizing a stochastic model to characterize pedestrian dynamics within the venue. Our model comprises a system of n agents moving across an underlying square lattice of size l representing the nightclub venue. Each agent can exist in one of three states: thirsty, served, or dancing. The dynamics governing the state changes are influenced by a memory time, denoted as τ, which reflects their drinking habits. Agents' movement throughout the lattice is controlled by a parameter α which measures the impetus towards/away from the bar. When α = 0, a power-law distribution emerges due to the non-objectivity of the agents. As α moves into intermediate values, an exponential behavior is observed, as it becomes possible to mitigate the drastic jamming effects in this scenario. However, for higher α values, the power-law distribution resurfaces due to increased jamming. We also demonstrate that the average concentration of served, thirsty, and dancing agents provide a reliable indicator of when the system reaches a jammed state. Subsequently, we construct a comprehensive map of the system's stationary state, supporting the idea that for high densities, α is not relevant, but for lower densities, the optimal values of measurements occurs at high values of α. To complete the analysis, we evaluate the conditional persistence, which measures the probability of an agent failing to receive their drink despite attempting to do so. In addition to contributing to the field of pedestrian dynamics, the present results serve as valuable indicators to assist commercial establishments in providing better services to their clients, tailored to the average drinking habits of their customers.

physics.soc-ph↗

arXiv2023

Exploring Crossing Times and Congestion Patterns at Scramble Intersections in Pedestrian Dynamics Models: A Statistical Analysis

Scramble intersections stand as compelling examples of complex systems, shedding light on the pressing challenge of urban mobility. In this paper, we introduce a model aimed at unraveling the statistical intricacies of pedestrian crossing times and their fluctuations in scenarios commonly encountered in major urban centers. Our findings offer snapshots that faithfully mirror real-world situations. Significantly, our results underscore the importance of two key factors: pedestrian flexibility and population density. These factors play a pivotal role in triggering the transition between mobile and immobile behavior in the steady state, a concept expounded upon within this paper through a straightforward order parameter known as directed mobility.

physics.soc-ph↗

arXiv2021

A physics-based algorithm to perform predictions in football leagues

In this work, we extended a stochastic model for football leagues based on the team's potential [R. da Silva et al. Comput. Phys. Commun. \textbf{184} 661--670 (2013)] for making predictions instead of only performing a successful characterization of the statistics on the punctuation of the real leagues. Our adaptation considers the advantage of playing at home when considering the potential of the home and away teams. The algorithm predicts the tournament's outcome by using the market value or/and the ongoing team's performance as initial conditions in the context of Monte Carlo simulations. We present and compare our results to the worldwide known SPI predictions performed by the "FiveThirtyEight" project. The results show that the algorithm can deliver good predictions even with a few ingredients and in more complicated seasons like the 2020 editions where the matches were played without fans in the stadiums.

physics.soc-ph↗

arXiv2019

Numerical study of condensation in a Fermi-like model of conterflowing particles via Gini coefficient

The collective motion of self-driven particles shows interesting novel phenomena such as swarming and the emergence of patterns. We have recently proposed a model for counterflowing particles that captures this idea and exhibits clogging transitions. This model is based on a generalization of the Fermi-Dirac statistics wherein the maximal occupation of a cell is used. Here we present a detailed study comparing synchronous and asynchronous stochastic dynamics within this model. We show that an asynchronous updating scheme supports the mobile-clogging transition and eliminates some mobility anomalies that are present in synchronous Monte Carlo simulations. Moreover, we show that this transition is dependent upon its initial conditions. Although the Gini coefficient was originally used to model wealth inequalities, we show that it is also efficient for studying the mobile-clogging transition. Finally, we compare our stochastic simulation with direct numerical integration of partial differential equations used to describe this model.

cond-mat.stat-mech↗

arXiv2019

Mobile-clogging transition in a Fermi-like model of counterflowing particles

In this paper we propose a generalized model for the motion of a two-species self-driven objects ranging from a scenario of a completely random environment of particles of negligible excluded volume to a more deterministic regime of rigid objects in an environment. Each cell of the system has a maximum occupation level called $σ_{\max }$. Both species move in opposite directions. The probability of any given particle to move to a neighboring cell depends on the occupation of this cell according to a Fermi-Dirac like distribution, considering a parameter $α$ that controls the system randomness. We show that for a certain $α=α_{c}$ the system abruptly transits from a mobile scenario to a clogged state which is characterized by condensates. We numerically describe the details of this transition by coupled partial differential equations (PDE) and Monte Carlo (MC) simulations that are in good agreement.

cond-mat.stat-mech↗

arXiv2016

Towards Rock-paper-scissors patterns in the Optional Public Goods Game under random mobility

Social dilemmas concern a natural conflict between cooperation and self interests among individuals in large populations. The emergence of cooperation and its maintenance is the key for the understanding of fundamental concepts about the evolution of species. In order to understand the mechanisms involved in this framework, here we study the Optional Public Good Games with focus on the effects of diffusive aspects in the emergent patterns of cyclic dominance between the strategies. Differently from other works, we showed that rock-paper-scissors (RPS) patterns occur by introducing a simple kind of random mobility in a lattice sparsely occupied. Such pattern has been revealed to be very important in the conservation of the species in ecological and social environments. The goal of this paper is to show that we do not need more elaborated schemes for construction of the neighbourhood in the game to observe RPS patterns as suggested in the literature. As an interesting additional result, in this contribution we also propose an alternative method to quantify the RPS density in a quantitative context of the game theory which becomes possible to perform a finite size scaling study. Such approach can be very interesting to be applied in other games generically.

physics.soc-ph↗