arXiv subjects

Silvio C. Ferreira

Publications and source records attributed to Silvio C. Ferreira.

62 records · Page 4Linked to original sources

arXiv2012

Epidemic thresholds of the Susceptible-Infected-Susceptible model on networks: A comparison of numerical and theoretical results

Recent work has shown that different theoretical approaches to the dynamics of the Susceptible-Infected-Susceptible (SIS) model for epidemics lead to qualitatively different estimates for the position of the epidemic threshold in networks. Here we present large-scale numerical simulations of the SIS dynamics on various types of networks, allowing the precise determination of the effective threshold for systems of finite size N. We compare quantitatively the numerical thresholds with theoretical predictions of the heterogeneous mean-field theory and of the quenched mean-field theory. We show that the latter is in general more accurate, scaling with N with the correct exponent, but often failing to capture the correct prefactor.

cond-mat.stat-mech↗

arXiv2011

Quasi-stationary simulations of the contact process on quenched networks

We present high-accuracy quasi-stationary (QS) simulations of the contact process in quenched networks, built using the configuration model with both structural and natural cutoffs. The critical behavior is analyzed in the framework of the anomalous finite size scaling which was recently shown to hold for the contact process on annealed networks. It turns out that the quenched topology does not qualitatively change the critical behavior, leading only (as expected) to a shift of the transition point. The anomalous finite size scaling holds with exactly the same exponents of the annealed case, so that we can conclude that heterogeneous mean-field theory works for the contact process on quenched networks, at odds with previous claims. Interestingly, topological correlations induced by the presence of the natural cutoff do not alter the picture.

cond-mat.stat-mech↗

arXiv2011

Scaling laws in the diffusion limited aggregation of persistent random walkers

We investigate the diffusion limited aggregation of particles executing persistent random walks. The scaling properties of both random walks and large aggregates are presented. The aggregates exhibit a crossover between ballistic and diffusion limited aggregation models. A non-trivial scaling relation $ξ\sim\ell^{1.25}$ between the characteristic size $ξ$, in which the cluster undergoes a morphological transition, and the persistence length $\ell$, between ballistic and diffusive regimes of the random walk, is observed.

cond-mat.stat-mech↗

arXiv2011

Quasi-stationary analysis of the contact process on annealed scale-free networks

We present an analysis of the quasi-stationary (QS) state of the contact process (CP) on annealed scale-free networks using a mapping of the CP dynamics in a one-step processes and analyzing numerically and analytically the corresponding master equation. The relevant QS quantities determined via the master equation exhibit an excellent agreement with direct QS stochastic simulations of the CP. The high accuracy of the resulting data allows to probe the strong corrections to scaling present in both the critical and supercritical regions, corrections that mask the correct finite size scaling obtained analytically by applying an exact heterogeneous mean-field approach. {Our results represent a promising starting point for a deeper understanding of the contact process and absorbing phase transitions on real (quenched) complex networks

cond-mat.stat-mech↗

arXiv2011

Faceted anomalous scaling in the epitaxial growth of semiconductor films

We apply the generic dynamical scaling theory (GDST) to the surfaces of CdTe polycrystalline films grown in glass substrates. The analysed data were obtained with a stylus profiler with an estimated resolution lateral resolution of $l_c=0.3 μ$m. Both real two-point correlation function and power spectrum analyses were done. We found that the GDST applied to the surface power spectra foresees faceted morphology in contrast with the self-affine surface indicated by the local roughness exponent found via the height-height correlation function. This inconsistency is explained in terms of convolution effects resulting from the finite size of the probe tip used to scan the surfaces. High resolution AFM images corroborates the predictions of GDST.

cond-mat.stat-mech↗

arXiv2011

Addendum to "Anomalous scaling and super-roughness in the growth of CdTe polycrystalline films"

The scaling of the growth of CdTe films on glass substrates was investigated by Mata \textit{et al.} [Phys. Rev. B \textbf{78}, 115305 (2008)]. Part of the analysis consisted of the estimation of the correlation length $ξ$ using the decay in the height-height correlation function. Afterwards, the dynamical exponent $z$ was determined using the scaling hypothesis $ξ\sim t^{1/z}$. In this Addendum, we show that the correlation lengths obtained by Mata \textit{et al.} provide a long wavelength coarsening exponent that does not correspond to the dynamical exponent $z$. We also show that the short wavelength coarsening exponent is consistent with the exponent $z$ obtained by Nascimento \textit{et al}. [arXiv:1101.1493] via generic dynamical scaling theory.

cond-mat.mtrl-sci↗

arXiv2011

Critical behavior of the contact process in a multiscale network

Inspired by dengue and yellow fever epidemics, we investigated the contact process (CP) in a multiscale network constituted by one-dimensional chains connected through a Barabási-Albert scale-free network. In addition to the CP dynamics inside the chains, the exchange of individuals between connected chains (travels) occurs at a constant rate. A finite epidemic threshold and an epidemic mean lifetime diverging exponentially in the subcritical phase, concomitantly with a power law divergence of the outbreak's duration, were found. A generalized scaling function involving both regular and SF components was proposed for the quasistationary analysis and the associated critical exponents determined, demonstrating that the CP on this hybrid network and nonvanishing travel rates establishes a new universality class.

physics.soc-ph↗

arXiv2011

Universality of the contact process with random dilution

We present quasi-stationary simulations of the two-dimensional contact process with quenched disorder included through the random dilution of a fraction of the lattice sites (these sites are not susceptible to infection). Our results strongly indicate that the static exponents are independent of the immunization fraction. In addition, the critical moment ratios $m=<ρ^2>/<ρ>^2$ deviate from the universal ratio $m=1.328$, observed for the non-dilluted system, to smaller values due to rare favorable regions which dominate the statistics.

cond-mat.stat-mech↗