Prof. Silvio Ferreira


A. J. Pereira, S. G. Alves, S. C. Ferreira, Effects of a kinetic barrier on limited-mobility interface growth models, arXiv:1902.03211

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We investigate discrete growth models for MBE where the particles moving from the top to the bottom of a terrace follows a random walk instead going directly as usually done. This effectively produces a probability to move downward that plays the role of a step barrier. We see that this simple mechanism is sufficient to destabilize the surface and produce 3d structures in the form of mounds. Figure shows surfaces generated with the Wolf-Villain model considering (right) or not (left) this purely kinetic step barrier.

W. Cota, S. C. Ferreira, R. Pastor-Satorras, and M. Starnini, Quantifying echo chamber effects in information spreading over political communication networks, arXiv:1901.03688

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We quantify the effects of echo chambers on the diffusion of information over online communication networks, characterizing the debate about the impeachment process of former Brazilian President Dilma Rousseff. We estimate the capability of users to spread the content they produce, showing that individuals broadcasting pro-impeachment sentiments can break their echo chamber, by reaching a larger and more diverse audience than other users. Figure shows the aggregated network of users expressing majorly pro-impeachment (blue), neutral (white), and anti-impeachment (red) sentiments in the content produced by them.

Recent papers

E. E. M. Luis, T. A. de Assis, S. C. Ferreira, and R. F. S. Andrade, Local roughness exponent in the nonlinear molecular-beam-epitaxy universality class in one-dimension, Phys. Rev. E 99 022801 (2019).

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We report local roughness exponents for three different models of surface kinetic roughening which belong to the non-linear molecular beam epitaxy universality class for. Our estimates shows that all investigated models present asymptotic non-anomalous scaling with local roughness exponent consistent with the VLDS equation in two-loop renormalization group analysis.

D. H. Silva, S. C. Ferreira, Activation thresholds in epidemic spreading with motile infectious agents on scale-free networks, Chaos 28, 123112 (2018).

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We analyze the effects of two diffusion rules, with and without preference to move towards higher degree vertices, on the epidemic SIS model on scale-free networks. We found standard diffusion yield an optimum diffusion rate, in which the threshold is minimum. Preferential diffusion remarkably changes the activation threshold in both analytical approximations and simulations. Figure shows the dependence with diffusion rate for standard (inset) and preferential (main) models.

S. N Santalla, S. C Ferreira, Eden model with nonlocal growth rules and the kinetic roughening in biological systems, Phys. Rev. E 98, 022405 (2018).

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We discuss the effects of non-locality on the growth of non-equilibrium aggregates using a parameter that mimics the effects of nutrient scarcity. The figure shows clusters obtained for three levels of nutrient scarcity.

W. Cota, A. S. Mata, S. C. Ferreira Robustness and fragility of the susceptible-infected-susceptible epidemic models on complex networks, Phys. Rev. E 98, 012310 (2018)

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Variations of the standard SIS models on scale-free networks are investigated. We observe that, depending on the level of heterogeneity of the network, these modified models can behave very differently from the standard one even though all present the same mean-field picture. Figure schematically shows some differences among the models.

W. Cota, G. Ódor, S. C. Ferreira, Griffiths phases in infinite-dimensional, non-hierarchical modular networks, Scientific Reports 8, 9144 (2018)

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We investigate the dynamics of the SIS model on modular networks with loosely connected modules. We observe the presence of extended regions where the dynamics is critical in a so-called Griffths phases illustrated in the figure. Our results can aid the understanding of critical behavior of the brain.