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Search Results: 1 - 10 of 29514 matches for " Rodrigo Frehse Pereira "
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Periodic orbit analysis at the onset of the unstable dimension variability and at the blowout bifurcation
Rodrigo Frehse Pereira,Sandro Ely de Souza Pinto,Ricardo L. Viana,Sergio R. Lopes,Celso Grebogi
Physics , 2009, DOI: 10.1063/1.2748619
Abstract: Many chaotic dynamical systems of physical interest present a strong form of nonhyperbolicity called unstable dimension variability (UDV), for which the chaotic invariant set contains periodic orbits possessing different numbers of unstable eigendirections. The onset of UDV is usually related to the loss of transversal stability of an unstable fixed point embedded in the chaotic set. In this paper, we present a new mechanism for the onset of UDV, whereby the period of the unstable orbits losing transversal stability tends to infinity as we approach the onset of UDV. This mechanism is unveiled by means of a periodic orbit analysis of the invariant chaotic attractor for two model dynamical systems with phase spaces of low dimensionality, and seems to depend heavily on the chaotic dynamics in the invariant set. We also described, for these systems, the blowout bifurcation (for which the chaotic set as a whole loses transversal stability) and its relation with the situation where the effects of UDV are the most intense. For the latter point, we found that chaotic trajectories off, but very close to, the invariant set exhibit the same scaling characteristic of the so-called on-off intermittency.
Periodic-orbit analysis and scaling laws of intermingled basins of attraction in an ecological dynamical system
Rodrigo Frehse Pereira,Sabrina Camargo,Sandro Ely de Souza Pinto,Sergio R. Lopes,Ricardo L. Viana
Physics , 2009, DOI: 10.1103/PhysRevE.78.056214
Abstract: Chaotic dynamical systems with two or more attractors lying on invariant subspaces may, provided certain mathematical conditions are fulfilled, exhibit intermingled basins of attraction: Each basin is riddled with holes belonging to basins of the other attractors. In order to investigate the occurrence of such phenomenon in dynamical systems of ecological interest (two-species competition with extinction) we have characterized quantitatively the intermingled basins using periodic-orbit theory and scaling laws. The latter results agree with a theoretical prediction from a stochastic model, and also with an exact result for the scaling exponent we derived for the specific class of models investigated. We discuss the consequences of the scaling laws in terms of the predictability of a final state (extinction of either species) in an ecological experiment.
Synchronization time in a hyperbolic dynamical system with long-range interactions
Rodrigo Frehse Pereira,Sandro Ely de Souza Pinto,Sergio Roberto Lopes
Physics , 2010, DOI: 10.1016/j.physa.2010.06.051
Abstract: We show that the threshold of complete synchronization in a lattice of coupled non-smooth chaotic maps is determined by linear stability along the directions transversal to the synchronization subspace. We examine carefully the sychronization time and show that a inadequate observation of the system evolution leads to wrong results. We present both careful numerical experiments and a rigorous mathematical explanation confirming this fact, allowing for a generalization involving hyperbolic coupled map lattices.
Chaos synchronization in a hyperbolic dynamical system with long-range interactions
Rodrigo Frehse Pereira,Sandro Ely de Souza Pinto,Ricardo Luiz Viana,Sergio Roberto Lopes
Physics , 2008,
Abstract: We show that the threshold of complete synchronization in a lattice of coupled non-smooth chaotic maps is determined by linear stability along the directions transversal to the synchronization subspace. As a result, the numerically determined synchronization threshold agree with the analytical results previously obtained [C. Anteneodo et al., Phys. Rev. E 68, 045202(R) (2003)] for this class of systems. We present both careful numerical experiments and a rigorous mathematical explanation confirming this fact, allowing for a generalization involving hyperbolic coupled map lattices.
Effective dynamics for chaos synchronization in networks with time-varying topology
Rodrigo Frehse Pereira,Romeu Miqueias Szmoski,Sandro Ely de Souza Pinto
Physics , 2010,
Abstract: A coupled map lattice whose topology changes at each time step is studied. We show that the transversal dynamics of the synchronization manifold can be analyzed by the introduction of effective dynamical quantities. These quantities are defined as weighted averages over all possible topologies. We demonstrate that an ensemble of short time observations can be used to predict the long-term behavior of the lattice. Finally, we point out that it is possible to obtain a lattice with constant topology in which the dynamical behavior is asymptotically identical to one of the time-varying topology.
Riddling and chaotic synchronization of coupled piecewise-linear Lorenz maps
Marcos C. Verges,Rodrigo Frehse Pereira,Sergio R. Lopes,Ricardo L. Viana,Tomasz Kapitaniak
Physics , 2009, DOI: 10.1016/j.physa.2009.02.015
Abstract: We investigate the parametric evolution of riddled basins related to synchronization of chaos in two coupled piecewise-linear Lorenz maps. Riddling means that the basin of the synchronized attractor is shown to be riddled with holes belonging to another basin in an arbitrarily fine scale, which has serious consequences on the predictability of the final state for such a coupled system. We found that there are wide parameter intervals for which two piecewise-linear Lorenz maps exhibit riddled basins (globally or locally), which indicates that there are riddled basins in coupled Lorenz equations, as previously suggested by numerical experiments. The use of piecewise-linear maps makes it possible to prove rigorously the mathematical requirements for the existence of riddled basins.
Locking-time and Information Capacity in CML with Statistical Periodicity
Romeu Miqueias Szmoski,Rodrigo Frehse Pereira,Fabiano Alan Serafim Ferrari,Sandro Ely de Souza Pinto
Physics , 2010,
Abstract: In this work we address the statistical periodicity phenomenon on a coupled map lattice. The study was done based on the asymptotic binary patterns. The pattern multiplicity gives us the lattice information capacity, while the entropy rate allows us to calculate the locking-time. Our results suggest that the lattice has low locking-time and high capacity information when the coupling is weak. This is the condition for the system to reproduce a kind of behavior observed in neural networks.
Parametric evolution of unstable dimension variability in coupled piecewise-linear chaotic maps
Rodrigo Frehse Pereira,Marcos C. Verges,Ricardo L. Viana,Sergio R. Lopes,Sandro Ely de Souza Pinto
Physics , 2010,
Abstract: In presence of unstable dimension variability numerical solutions of chaotic systems are valid only for short periods of observation. For this reason, analytical results for systems that exhibit this phenomenon are needed. Aiming to go one step further in obtaining such results, we study the parametric evolution of unstable dimension variability in two coupled bungalow maps. Each of these maps presents intervals of linearity that define Markov partitions, which are recovered for the coupled system in the case of synchronization. Using such partitions we find exact results for the onset of unstable dimension variability and for contrast measure, which quantifies the intensity of the phenomenon in terms of the stability of the periodic orbits embedded in the synchronization subspace.
U-topias (urbanas) do pensamento sociológico
Frehse, Fraya;
Estudos Avan?ados , 2012, DOI: 10.1590/S0103-40142012000200013
Abstract: what do the places conceptualized in sociological thought reveal about the ways this discipline addresses hope? sociologists' hopes express themselves, among others, in representations of places that are envisaged as settings historically pregnant of other social orders. by focusing especially on urban u-topias brought about at the beginning of sociology in germany, france, the united states and brazil, and on their recent conceptual unfoldings, one realizes the methodological role that representations of time as to (urban) space play in the relations of sociology with hope. particularly historical concepts of time regarding cities seem to be crucial for a "hopeful" sociology.
Cart?es postais paulistanos da virada do século XX: problematizando a S?o Paulo "moderna"
Frehse, Fraya;
Horizontes Antropológicos , 2000, DOI: 10.1590/S0104-71832000000100007
Abstract: based on the fact that photographic postcards start to be edited in s?o paulo at the end of the 19th century, this article analyses if the cards, as modern iconographic documents in the paulistano past, basically propagated, to the society of that time, visual representations of a modern city par excellence - thus free from rural and slavish cultural references, which were brought about in its colonial past. in order to answer this question i evaluated the relation between sign and referent in postcard photographs of tramways in downtown s?o paulo in the turn of the 20th century by contextualizing the day-by-day experienced by pedestrians in the photographed streets . the study reveals that the common association between turn-of-the-century s?o paulo urban photographs and the image of a "modern" city is not a sufficient explanation if the aim is the comprehension of that society's own conception about the photographs, in that time.
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