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Jun 30, 2018
06/18

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Nuno Crokidakis

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In this work we study the critical behavior of a three-state ($+1$, $-1$, $0$) opinion model with independence. Each agent has a probability $q$ to act as independent, i.e., he/she can choose his/her opinion independently of the opinions of the other agents. On the other hand, with the complementary probability $1-q$ the agent interacts with a randomly chosen individual through a kinetic exchange. Our analytical and numerical results show that the independence mechanism acts as a noise that...

Topics: Physics, Statistical Mechanics, Physics and Society, Computing Research Repository, Social and...

Source: http://arxiv.org/abs/1404.4356

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Jun 30, 2018
06/18

by
Nuno Crokidakis

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In this work we study the critical behavior of a three-state opinion model in the presence of noise. This noise represents the independent behavior, that plays the role of social temperature. Each agent on a regular D-dimensional lattice has a probability $q$ to act as independent, i.e., he can choose his opinion independent of the opinions of his neighbors. Furthermore, with the complementary probability $1-q$ the agent interacts with a randomly chosen nearest neighbor through a kinetic...

Topics: Physics, Statistical Mechanics, Condensed Matter, Physics and Society

Source: http://arxiv.org/abs/1702.02061

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Sep 23, 2013
09/13

by
Nuno Crokidakis

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In this work we consider the influence of mass media in the dynamics of the two-dimensional Sznajd model. This influence acts as an external field, and it is introduced in the model by means of a probability $p$ of the agents to follow the media opinion. We performed Monte Carlo simulations on square lattices with different sizes, and our numerical results suggest a change on the critical behavior of the model, with the absence of the usual phase transition for $p>\sim 0.18$. Another effect...

Source: http://arxiv.org/abs/1111.5750v2

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Sep 22, 2013
09/13

by
Nuno Crokidakis

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We study a nonequilibrium Ising model that stochastically evolves under the simultaneous operation of several spin-flip mechanisms. In other words, the local magnetic fields change sign randomly with time due to competing kinetics. This dynamics models a fast and random diffusion of disorder that takes place in dilute metallic alloys when magnetic ions diffuse. We performe Monte Carlo simulations on cubic lattices up to L=60. The system exhibits ferromagnetic and paramagnetic steady states. Our...

Source: http://arxiv.org/abs/1004.2065v1

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Jun 30, 2018
06/18

by
Nuno Crokidakis

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In this work we study the problem of tax evasion on a fully-connected population. For this purpose, we consider that the agents may be in three different states, namely honest tax payers, tax evaders and undecided, that are individuals in an intermediate class among honests and evaders. Every individual can change his/her state following a kinetic exchange opinion dynamics, where the agents interact by pairs with competitive negative (with probability $q$) and positive (with probability $1-q$)...

Topics: Physics, Physics and Society, Computing Research Repository, Social and Information Networks

Source: http://arxiv.org/abs/1407.5220

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Jun 28, 2018
06/18

by
Nuno Crokidakis

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In this work we study a 3-state opinion formation model considering two distinct mechanisms, namely independence and conviction. Independence is introduced in the model as a noise, by means of a probability of occurrence $q$. On the other hand, conviction acts as a disorder in the system, and it is introduced by two discrete probability distributions. We analyze the effects of such two mechanisms on the phase transitions of the model, and we found that the critical exponents are universal over...

Topics: Physics and Society, Physics

Source: http://arxiv.org/abs/1512.00257

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Jun 30, 2018
06/18

by
Nuno Crokidakis; Edgardo Brigatti

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In this work we study on a 2-dimensional square lattice a recent version of the Naming Game, an agent-based model used for describing the emergence of linguistic structures. The system is open-ended and agents can invent new words all along the evolution of the game, picking them up from a pool characterised by a Gaussian distribution with standard deviation $\sigma$. The model displays a nonequilibrium phase transition at a critical point $\sigma_{c}\approx 25.6$, which separates an absorbing...

Topics: Physics, Statistical Mechanics, Physics and Society, Computing Research Repository, Social and...

Source: http://arxiv.org/abs/1412.2994

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Jun 30, 2018
06/18

by
Celia Anteneodo; Nuno Crokidakis

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We study the critical behavior of a continuous opinion model, driven by kinetic exchanges in a fully-connected population. Opinions range in the real interval $[-1,1]$, representing the different shades of opinions against and for an issue under debate. Individual's opinions evolve through pairwise interactions, with couplings that are typically positive, but a fraction $p$ of negative ones is allowed. Moreover, a social temperature parameter $T$ controls the tendency of the individual...

Topics: Physics, Statistical Mechanics, Condensed Matter, Physics and Society

Source: http://arxiv.org/abs/1703.07451

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Sep 18, 2013
09/13

by
Nuno Crokidakis; Celia Anteneodo

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We analyze the critical behavior of a class of discrete opinion models in the presence of disorder. Within this class, each agent opinion takes a discrete value ($\pm 1$ or 0) and its time evolution is ruled by two terms, one representing agent-agent interactions and the other the degree of conviction or persuasion (a self-interaction). The mean-field limit, where each agent can interact evenly with any other, is considered. Disorder is introduced in the strength of both interactions, with...

Source: http://arxiv.org/abs/1209.5683v2

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Jun 30, 2018
06/18

by
Fabricio L. Forgerini; Nuno Crokidakis

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We study the competition and the evolution of nodes embedded in Euclidean restricted spaces. The population evolves by a branching process in which new nodes are generated when up to two new nodes are attached to the previous ones at each time unit. The competition in the population is introduced by considering the effect of overcrowding of nodes in the embedding space. The branching process is suppressed if the newborn node is closer than a distance $\xi$ of the previous nodes. This rule may...

Topics: Populations and Evolution, Quantitative Biology, Statistical Mechanics, Condensed Matter

Source: http://arxiv.org/abs/1406.3316

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Jun 28, 2018
06/18

by
Allan R. Vieira; Nuno Crokidakis

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In this work we study the majority-vote model with the presence of two distinc noises. The first one is the usual noise $q$, that represents the probability that a given agent follows the minority opinion of his/her social contacts. On the other hand, we consider the independent behavior, such that an agent can choose his/her own opinion $+1$ or $-1$ with equal probability, independent of the group's norm. We study the impact of the presence of such two kinds of stochastic driving in the phase...

Topics: Physics and Society, Statistical Mechanics, Condensed Matter, Physics

Source: http://arxiv.org/abs/1511.05111

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Sep 23, 2013
09/13

by
Nuno Crokidakis; Fabricio L. Forgerini

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In this work we study a modified version of the Sznajd sociophysics model. In particular we introduce reputation, a mechanism that limits the capacity of persuasion of the agents. The reputation is introduced as a score which is time-dependent, and its introduction avoid dictatorship (all spins parallel) for a wide range of parameters. The relaxation time follows a log-normal-like distribution. In addition, we show that the usual phase transition also occurs, as in the standard model, and it...

Source: http://arxiv.org/abs/1006.2456v2

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Jun 29, 2018
06/18

by
Marcelo A. Pires; Nuno Crokidakis

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In this work we consider a model of epidemic spreading coupled with an opinion dynamics in a fully-connected population. Regarding the opinion dynamics, the individuals may be in two distinct states, namely in favor or against a vaccination campaign. Individuals against the vaccination follow a standard SIS model, whereas the pro-vaccine individuals can also be in a third compartment, namely Vaccinated. In addition, the opinions change according to the majority-rule dynamics in groups with...

Topics: Physics and Society, Statistical Mechanics, Condensed Matter, Physics, Quantitative Biology,...

Source: http://arxiv.org/abs/1605.03914

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Jun 29, 2018
06/18

by
Allan R. Vieira; Nuno Crokidakis

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In this work we study a 3-state ($+1$, $-1$, $0$) opinion model in the presence of noise and disorder. We consider pairwise competitive interactions, with a fraction $p$ of those interactions being negative (disorder). Moreover, there is a noise $q$ that represents the probability of an individual spontaneously change his opinion to the neutral state. Our aim is to study how the increase/decrease of the fraction of neutral agents affects the critical behavior of the system and the evolution of...

Topics: Statistical Mechanics, Condensed Matter, Physics, Physics and Society

Source: http://arxiv.org/abs/1606.04058

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Sep 24, 2013
09/13

by
Nuno Crokidakis; Fabricio L. Forgerini

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We propose a modification in the Sznajd sociophysics model defined on the square lattice. For this purpose, we consider reputation-a mechanism limiting the agents' persuasive power. The reputation is introduced as a time-dependent score, which can be positive or negative. This mechanism avoids dictatorship (full consensus, all spins parallel) for a wide range of model parameters. We consider two different situations: case 1, in which the agents' reputation increases for each persuaded neighbor,...

Source: http://arxiv.org/abs/1112.6108v1

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Jun 27, 2018
06/18

by
Nuno Crokidakis; Paulo Murilo Castro de Oliveira

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In this work we study opinion formation in a population participating of a public debate with two distinct choices. We considered three distinct mechanisms of social interactions and individuals' behavior: conformity, nonconformity and inflexibility. The conformity is ruled by the majority-rule dynamics, whereas the nonconformity is introduced in the population as an independent behavior, implying the failure to attempted group influence. Finally, the inflexible agents are introduced in the...

Topics: Social and Information Networks, Physics and Society, Statistical Mechanics, Physics, Condensed...

Source: http://arxiv.org/abs/1505.05163

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Sep 23, 2013
09/13

by
Marlon Ramos; Nuno Crokidakis; Celia Anteneodo

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We study the critical properties of a model of information spreading based on the SIS epidemic model. Spreading rates decay with time, as ruled by two parameters, $\epsilon$ and $l$, that can be either constant or randomly distributed in the population. The spreading dynamics is developed on top of Erd\"os-Renyi networks. We present the mean-field analytical solution of the model in its simplest formulation, and Monte Carlo simulations are performed for the more heterogeneous cases. The...

Source: http://arxiv.org/abs/1212.2547v1

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Sep 21, 2013
09/13

by
Nuno Crokidakis; Paulo Murilo Castro de Oliveira

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In this work we study a modified version of the two-dimensional Sznajd sociophysics model. In particular, we consider the effects of agents' reputations in the persuasion rules. In other words, a high-reputation group with a common opinion may convince their neighbors with probability $p$, which induces an increase of the group's reputation. On the other hand, there is always a probability $q=1-p$ of the neighbors to keep their opinions, which induces a decrease of the group's reputation. These...

Source: http://arxiv.org/abs/1108.5934v2

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Sep 20, 2013
09/13

by
Nuno Crokidakis; Silvio M. Duarte Queiros

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In this work, we inspect the reliability of controlling and quelling an epidemic disease mimicked by a Susceptible-Infected-Susceptible (SIS) model defined on a complex network by means of current and implementable quarantine and isolation policies. Specifically, we consider that each individual in the network is originally linked to two types of individuals: members of the same household and acquaintances. The topology of this network evolves taking into account a probability $q$ that aims at...

Source: http://arxiv.org/abs/1205.3337v1

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Sep 23, 2013
09/13

by
Nuno Crokidakis; Marcio Argollo de Menezes

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We study numerically a model of nonequilibrium networks where nodes and links are added at each time step with aging of nodes and connectivity- and age-dependent attachment of links. By varying the effects of age in the attachment probability we find, with numerical simulations and scaling arguments, that a giant cluster emerges at a first-order critical point and that the problem is in the universality class of one dimensional percolation. This transition is followed by a change in the giant...

Source: http://arxiv.org/abs/0904.1517v2

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Jul 20, 2013
07/13

by
Nuno Crokidakis; Marcio Argollo de Menezes

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In this work we study a modified Susceptible-Infected-Susceptible (SIS) model in which the infection rate $\lambda$ decays exponentially with the number of reinfections $n$, saturating after $n=l$. We find a critical decaying rate $\epsilon_{c}(l)$ above which a finite fraction of the population becomes permanently infected. From the mean-field solution and computer simulations on hypercubic lattices we find evidences that the upper critical dimension is 6 like in the SIR model, which can be...

Source: http://arxiv.org/abs/1203.6673v1

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Jun 30, 2018
06/18

by
Angelo Mondaini Calvão; Nuno Crokidakis; Celia Anteneodo

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Elections, specially in countries such as Brazil with an electorate of the order of 100 million people, yield large-scale data-sets embodying valuable information on the dynamics through which individuals influence each other and make choices. In this work we perform an extensive analysis of data sets available for Brazilian proportional elections of legislators and city councillors throughout the period 1970-2012, which embraces two distinct political regimes: a military dictatorship and a...

Topics: Physics, Data Analysis, Statistics and Probability, Statistical Mechanics, Physics and Society,...

Source: http://arxiv.org/abs/1406.6322

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Jun 29, 2018
06/18

by
Allan R. Vieira; Celia Anteneodo; Nuno Crokidakis

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We investigate opinion formation in a kinetic exchange opinion model, where opinions are represented by numbers in the real interval $[-1,1]$ and agents are typified by the individual degree of conviction about the opinion that they support. Opinions evolve through pairwise interactions governed by competitive positive and negative couplings, that promote imitation and dissent, respectively. The model contemplates also another type of nonconformity such that agents can occasionally choose their...

Topics: Physics and Society, Statistical Mechanics, Condensed Matter, Physics, Computing Research...

Source: http://arxiv.org/abs/1601.04460

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Jun 30, 2018
06/18

by
Nuno Crokidakis; Paulo Murilo Castro de Oliveira

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Street demonstrations occur across the world. In Rio de Janeiro, June/July 2013, they reach beyond one million people. A wrathful reader of \textit{O Globo}, leading newspaper in the same city, published a letter \cite{OGlobo} where many social questions are stated and answered Yes or No. These million people of street demonstrations share opinion consensus about a similar set of social issues. But they did not reach this consensus within such a huge numbered meetings. Earlier, they have met in...

Topics: Physics, Quantitative Biology, Statistical Mechanics, Physics and Society, Computing Research...

Source: http://arxiv.org/abs/1404.6993

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Jun 30, 2018
06/18

by
Nuno Crokidakis; Victor H. Blanco; Celia Anteneodo

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In this work we study opinion formation on a fully-connected population participating of a public debate with two distinct choices, where the agents may adopt three different attitudes (favorable to either one choice or to the other, or undecided). The interactions between agents occur by pairs and are competitive, with couplings that are either negative with probability $p$ or positive with probability $1-p$. This bimodal probability distribution of couplings produces a behavior similar to the...

Topics: Physics, Statistical Mechanics, Physics and Society, Computing Research Repository, Social and...

Source: http://arxiv.org/abs/1401.2880

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Sep 21, 2013
09/13

by
Nuno Crokidakis; Silvio M. Duarte Queiros

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Using a single functional form which is able to represent several different classes of statistical distributions, we introduce a preliminary study of the ferromagnetic Ising model on the cubic lattices under the influence of non-Gaussian local external magnetic field. Specifically, depending on the value of the tail parameter, $\tau $ ($\tau < 3$), we assign a quenched random field that can be platykurtic (sub-Gaussian) or leptokurtic (fat-tailed) form. For $\tau < 5/3$, such...

Source: http://arxiv.org/abs/1011.3337v1

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Sep 22, 2013
09/13

by
Silvio M. Duarte Queiros; Nuno Crokidakis; Diogo O. Soares-Pinto

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The influence of the tail features of the local magnetic field probability density function (PDF) on the ferromagnetic Ising model is studied in the limit of infinite range interactions. Specifically, we assign a quenched random field whose value is in accordance with a generic distribution that bears platykurtic and leptokurtic distributions depending on a single parameter $\tau < 3$ to each site. For $\tau < 5/3$, such distributions, which are basically Student-$t$ and $r$-distribution...

Source: http://arxiv.org/abs/0906.5602v1

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Sep 22, 2013
09/13

by
Octavio R. Salmon; Nuno Crokidakis; Fernando D. Nobre

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A random-field Ising model that is capable of exhibiting a rich variety of multicritical phenomena, as well as a smearing of such behavior, is investigated. The model consists of an infinite-range-interaction Ising ferromagnet in the presence of a triple-Gaussian random magnetic field, which is defined as a superposition of three Gaussian distributions with the same width $\sigma$, centered at H=0 and $H=\pm H_{0}$, with probabilities $p$ and $(1-p)/2$, respectively. Such a distribution is very...

Source: http://arxiv.org/abs/0812.2585v1