arXiv subjects

M. A. F. Gomes

Publications and source records attributed to M. A. F. Gomes.

9 recordsLinked to original sources

arXiv2016

Crumpling Damaged Graphene

Through molecular mechanics we find that non-covalent interactions modify the fractality of crumpled damaged graphene. Pristine graphene membranes are damaged by adding random vacancies and carbon-hydrogen bonds. Crumpled membranes exhibit a fractal dimension of $ 2.71 \pm 0.02$ when all interactions between carbon atoms are considered, and $2.30 \pm 0.05$ when non-covalent interactions are suppressed. The transition between these two values, obtained by switching on/off the non-covalent interactions of equilibrium configurations, is shown to be reversible and independent on thermalisation. In order to explain this transition, we propose a theoretical model that is compatible with our numerical findings. Finally, we also compare damaged graphene membranes with other crumpled structures, as for instance, polymerised membranes and paper sheets, that share similar scaling properties.

cond-mat.mes-hall↗

arXiv2007

Model inspired by population genetics to study fragmentation of brittle plates

We use a model whose rules were inspired by population genetics, the random capability growth model, to describe the statistical details observed in experiments of fragmentation of brittle platelike objects, and in particular the existence of (i) composite scaling laws, (ii) small critical exponents τassociated with the power-law fragment-size distribution, and (iii) the typical pattern of cracks. The proposed computer simulations do not require numerical solutions of the Newton's equations of motion, nor several additional assumptions normally used in discrete element models. The model is also able to predict some physical aspects which could be tested in new experiments of fragmentation of brittle systems.

cond-mat.stat-mech↗

arXiv2007

Condensation of elastic energy in two-dimensional packing of wire

Forced packing of a long metallic wire injected into a two-dimensional cavity leads to crushed structures involving a hierarchical cascade of loops with varying curvature radii. We study the distribution of elastic energy stored in such systems from experiments, and high-resolution digital techniques. It is found that the set where the elastic energy of curvature is concentrated has dimension $D_\mathcal{S} = 1.0 \pm 0.1$, while the set where the mass is distributed, has dimension $D =1.9 \pm 0.1$.

cond-mat.stat-mech↗

arXiv2006

Anomalous diffusion on crumpled wires in two dimensions

It is investigated the statistical properties of random walks evolving on real configurations of a crumpled wire rigidly jammed in two dimensions. These crumpled hierarchical structures with complex topology are obtained from a metallic wire injected at a constant rate into a transparent planar cell of 20cm of diameter. The observed diffusion is anomalous with an exponent very close to that obtained at the threshold of two dimensional percolation. A comparison of the system studied in this paper with other systems of physical interest is also made, and an experimental consequence of our results is discussed.

cond-mat.stat-mech↗

arXiv2005

Theoretical model for the evolution of the linguistic diversity

Here we describe how some important scaling laws observed in the distribution of languages on Earth can emerge from a simple computer simulation. The proposed language dynamics includes processes of selective geographic colonization, linguistic anomalous diffusion and mutation, and interaction among populations that occupy different regions. It is found that the dependence of the linguistic diversity on the area after colonization displays two power law regimes, both described by critical exponents which are dependent on the mutation probability. Most importantly for the future prospect of world's population, our results show that the linguistic diversity always decrease to an asymptotic very small value if large areas and sufficiently long times of interaction among populations are considered.

physics.soc-ph↗

arXiv2005

Scaling relations for diversity of languages

The distribution of living languages is investigated and scaling relations are found for the diversity of languages as a function of the country area and population. These results are compared with data from Ecology and from computer simulations of fragmentation dynamics where similar scalings appear. The language size distribution is also studied and shown to display two scaling regions: (i) one for the largest (in population) languages and (ii) another one for intermediate-size languages. It is then argued that these two classes of languages may have distinct growth dynamics, being distributed on the sets of different fractal dimensions.

physics.soc-ph↗

arXiv2005

Nontrivial temporal scaling in a Galilean stick-slip dynamics

We examine the stick-slip fluctuating response of a rough massive non-rotating cylinder moving on a rough inclined groove which is submitted to weak external perturbations and which is maintained well below the angle of repose. The experiments presented here, which are reminiscent of the Galileo's works with rolling objects on inclines, have brought in the last years important new insights into the friction between surfaces in relative motion and are of relevance for earthquakes, differing from classical block-spring models by the mechanism of energy input in the system. Robust nontrivial temporal scaling laws appearing in the dynamics of this system are reported, and it is shown that the time-support where dissipation occurs approaches a statistical fractal set with a fixed value of dimension. The distribution of periods of inactivity in the intermittent motion of the cylinder is also studied and found to be closely related to the lacunarity of a random version of the classic triadic Cantor set on the line.

cond-mat.stat-mech↗

arXiv2004

Sliding susceptibility of a rough cylinder on a rough inclined perturbed surface

A susceptibility function $χ(L)$ is introduced to quantify some aspects of the intermittent stick-slip dynamics of a rough metallic cylinder of length $L$ on a rough metallic incline submitted to small controlled perturbations and maintained below the angle of repose. This problem is studied from the experimental point of view and the observed power-law behavior of $χ(L)$ is justified through the use of a general class of scaling hypotheses.

cond-mat.stat-mech↗

arXiv2004

Omori Law for Sliding of Blocks on Inclined Rough Surfaces

Long sequences of slidings of solid blocks on an inclined rough surface submitted to small controlled perturbations are examined and scaling relations are found for the time distribution of slidings between pairs of large events as well as after and before the largest events. These scaling laws are similar to the Omori law in seismology but the scaling exponents observed are different. Log-periodicity correction to the Omori scaling is also found. It is shown that the scaling behaviors are dependent on the angle that the incline forms with the horizontal.

cond-mat.stat-mech↗