Luis Reinaudi | Searcharxiv

arXiv2023

Contrarian Majority rule model with external oscillating propaganda and individual inertias

We study the Galam majority rule dynamics with contrarian behavior and an oscillating external propaganda, in a population of agents that can adopt one of two possible opinions. In an iteration step, a random agent interacts with other three random agents and takes the majority opinion among the agents with probability $p(t)$ (majority behavior) or the opposite opinion with probability $1-p(t)$ (contrarian behavior). The probability of following the majority rule $p(t)$ varies with the temperature $T$ and is coupled to a time-dependent oscillating field that mimics a mass media propaganda, in a way that agents are more likely to adopt the majority opinion when it is aligned with the sign of the field. We investigate the dynamics of this model on a complete graph and find various regimes as $T$ is varied. A transition temperature $T_c$ separates a bimodal oscillatory regime for $T T_c$ in which $m$ oscillates around zero. These regimes are characterized by the distribution of residence times that exhibits a unique peak for a resonance temperature $T^*$, where the response of the system is maximum. An insight into these results is given by a mean-field approach, which also shows that $T^*$ and $T_c$ are closely related.

physics.soc-ph↗

arXiv2022

Contrarian Voter Model under the influence of an Oscillating Propaganda: Consensus, Bimodal behavior and Stochastic Resonance

We study the contrarian voter model for opinion formation in a society under the influence of an external oscillating propaganda and stochastic noise. Each agent of the population can hold one of two possible opinions on a given issue --against or in favor, and interacts with its neighbors following either an imitation dynamics (voter behavior) or an anti-alignment dynamics (contrarian behavior): each agent adopts the opinion of a random neighbor with a time-dependent probability $p(t)$, or takes the opposite opinion with probability $1-p(t)$. The imitation probability $p(t)$ is controlled by the social temperature $T$, and varies in time according to a periodic field that mimics the influence of an external propaganda, so that a voter is more prone to adopt an opinion aligned with the field. We simulate the model in complete graph and in lattices, and find that the system exhibits a rich variety of behaviors as $T$ is varied: opinion consensus for $T=0$, a bimodal behavior for $T T_c$, and full disorder for $T \gg 1$. The transition temperature $T_c$ vanishes with the population size $N$ as $T_c \simeq 2/\ln N$ in complete graph. Besides, the distribution of residence times $t_r$ in the bimodal phase decays approximately as $t_r^{-3/2}$. Within the oscillatory regime, we find a stochastic resonance-like phenomenon at a given temperature $T^*$. Also, mean-field analytical results show that the opinion oscillations reach a maximum amplitude at an intermediate temperature, and that exhibit a lag respect to the field that decreases with $T$.

physics.soc-ph↗