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Sep 23, 2013
09/13

by
Tiago Pereira

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We give a succinct and self-contained description of the synchronized motion on networks of mutually coupled oscillators. Usually, the stability criterion for the stability of synchronized motion is obtained in terms of Lyapunov exponents. We consider the fully diffusive case which is amenable to treatment in terms of uniform contractions. This approach provides a rigorous, yet clear and concise, way to the important results.

Source: http://arxiv.org/abs/1112.2297v2

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6.0

Nov 6, 2018
11/18

by
Tiago Pereira

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Source: https://www.flickr.com/photos/33766395@N00/6342081214 Uploader: Tiago Pereira

Topics: Flickr, video

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33

Jul 19, 2013
07/13

by
Tiago Pereira

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Heterogeneity in the degree distribution is known to suppress global synchronization in complex networks of symmetrically coupled oscillators. Scale-free networks display a great deal of heterogeneity, containing a few nodes, termed hubs, that are highly connected, while most nodes receive only a few connections. Here, we show that a group of synchronized nodes may appear in scale-free networks: hubs undergo a transition to synchronization while the other nodes remain unsynchronized. This...

Source: http://arxiv.org/abs/1005.3803v3

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2.0

Jun 30, 2018
06/18

by
Tiago Pereira; Dmitry Turaev

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Fermi acceleration is the process of energy transfer from massive objects in slow motion to light objects that move fast. The model for such process is a time-dependent Hamiltonian system. As the parameters of the system change with time, the energy is no longer conserved, which makes the acceleration possible. One of the main problems is how to generate a sustained and robust energy growth. We show that the non-ergodicity of any chaotic Hamiltonian system must universally lead to the...

Topics: Nonlinear Sciences, Chaotic Dynamics

Source: http://arxiv.org/abs/1410.1722

2
2.0

Jun 30, 2018
06/18

by
Eduardo Garibaldi; Tiago Pereira

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We study the behavior of solutions of mutually coupled equations in heterogeneous random graphs. Heterogeneity means that some equations receive many inputs whereas most of the equations are given only with a few connections. Starting from a situation where the isolated equations are unstable, we prove that a heterogeneous interaction structure leads to the appearance of stable subspaces of solutions. Moreover, we show that, for certain classes of heterogeneous networks, increasing the strength...

Topics: Mathematics, Probability, Mathematical Physics, Dynamical Systems

Source: http://arxiv.org/abs/1409.5726

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3.0

Jun 27, 2018
06/18

by
Tiago Pereira; Dmitry Turaev

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Fermi acceleration is the process of energy transfer from massive objects in slow motion to light objects that move fast. The model for such process is a time-dependent Hamiltonian system. As the parameters of the system change with time, the energy is no longer conserved, which makes the acceleration possible. One of the main problems is how to generate a sustained and robust energy growth. We show that the non-ergodicity of any chaotic Hamiltonian system must universally lead to the...

Topics: Nonlinear Sciences, Chaotic Dynamics, Mathematics, Mathematical Physics

Source: http://arxiv.org/abs/1503.04691

2
2.0

Jun 30, 2018
06/18

by
Jan Philipp Pade; Tiago Pereira

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In many real-world networks the ability to synchronize is a key property for its performance. Examples include power-grid, sensor, and neuron networks as well as consensus formation. Recent work on undirected networks with diffusive interaction revealed that improvements in the network connectivity such as making the network more connected and homogeneous enhances synchronization. However, real-world networks have directed and weighted connections. In such directed networks, understanding the...

Topics: Physics, Nonlinear Sciences, Mathematics, Physics and Society, Adaptation and Self-Organizing...

Source: http://arxiv.org/abs/1408.4684

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2.0

Jun 30, 2018
06/18

by
Vladimir Vlasov; Yong Zou; Tiago Pereira

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Spontaneous explosive is an abrupt transition to collective behavior taking place in heterogeneous networks when the frequencies of the nodes are positively correlated to the node degree. This explosive transition was conjectured to be discontinuous. Indeed, numerical investigations reveal a hysteresis behavior associated with the transition. Here, we analyze explosive synchronization in star graphs. We show that in the thermodynamic limit the transition to (and out) collective behavior is...

Topics: Nonlinear Sciences, Mathematics, Adaptation and Self-Organizing Systems, Mathematical Physics,...

Source: http://arxiv.org/abs/1411.6873

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3.0

Jun 30, 2018
06/18

by
Jake Stroud; Mauricio Barahona; Tiago Pereira

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Experimental results often do not assess network structure; rather, the network structure is inferred by the dynamics of the nodes. From the dynamics of the nodes one then constructs a network of functional relations, termed the functional network. A fundamental question in the analysis of complex systems concerns the relation between functional and structural networks. Using synchronisation as a paradigm for network functionality, we study the dynamics of cluster formation in functional...

Topics: Nonlinear Sciences, Adaptation and Self-Organizing Systems

Source: http://arxiv.org/abs/1411.2805

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8.0

Jun 30, 2018
06/18

by
Deniz Eroglu; Jeroen Lamb; Tiago Pereira

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Dynamical networks are important models for the behaviour of complex systems, modelling physical, biological and societal systems, including the brain, food webs, epidemic disease in populations, power grids and many other. Such dynamical networks can exhibit behaviour in which deterministic chaos, exhibiting unpredictability and disorder, coexists with synchronization, a classical paradigm of order. We survey the main theory behind complete, generalized and phase synchronization phenomena in...

Topics: Chaotic Dynamics, Nonlinear Sciences

Source: http://arxiv.org/abs/1703.08296

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Sep 20, 2013
09/13

by
Jorrit Leenaarts; Tiago Pereira; Han Uitenbroek

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Radiative transfer modeling of spectral lines including partial redistribution (PRD) effects requires the evaluation of the ratio of the emission to the absorption profile. This quantity requires a large amount of computational work if one employs the angle-dependent redistribution function, which prohibits its use in 3D radiative transfer computations with model atmospheres containing velocity fields. We aim to provide a method to compute the emission to absorption profile ratio that requires...

Source: http://arxiv.org/abs/1205.5110v1

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Sep 22, 2013
09/13

by
Tiago Pereira; D. H. U. Marchetti

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We provide necessary and sufficient conditions for states to have an arbitrarily small uncertainty product of the azimuthal angle $\phi $ and its canonical moment $L_{z}$. We illustrate our results with analytical examples.

Source: http://arxiv.org/abs/0805.1331v2

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2.0

Jun 30, 2018
06/18

by
Camille Poignard; Tiago Pereira; Jan Philipp Pade

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This article deals with the spectra of Laplacians of weighted graphs. In this context, two objects are of fundamental importance for the dynamics of complex networks: the second eigenvalue of such a spectrum (called algebraic connectivity) and its associated eigenvector, the so-called Fiedler vector. Here we prove that, given a Laplacian matrix, it is possible to perturb the weights of the existing edges in the underlying graph in order to obtain simple eigenvalues and a Fiedler vector composed...

Topics: Spectral Theory, Mathematical Physics, Mathematics

Source: http://arxiv.org/abs/1704.01677

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2.0

Jun 30, 2018
06/18

by
Tiago Pereira; Sebastian van Strien; Matteo Tanzi

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The aim of this paper is to rigorously study dynamics of Heterogeneously Coupled Maps (HCM). Such systems are determined by a network with heterogeneous degrees. Some nodes, called hubs, are very well connected while most nodes interact with few others. The local dynamics on each node is chaotic, coupled with other nodes according to the network structure. Such high-dimensional systems are hard to understand in full, nevertheless we are able to describe the system over exponentially large time...

Topics: Dynamical Systems, Mathematics

Source: http://arxiv.org/abs/1704.06163

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4.0

Jun 30, 2018
06/18

by
Vittorio Perera; Tiago Pereira; Jonathan Connell; Manuela Veloso

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In this paper we present our work with the Pepper robot, a service robot from SoftBank Robotics. We had two main goals in this work: improving the autonomy of this robot by increasing its awareness of the environment; and enhance the robot ability to interact with its users. To achieve this goals, we used ROS, a modern open-source framework for developing robotics software, to provide Pepper with state of the art localization and navigation capabilities. Furthermore, we contribute an...

Topics: Computing Research Repository, Robotics

Source: http://arxiv.org/abs/1704.04797

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Jul 20, 2013
07/13

by
Tiago Pereira; Jaap Eldering; Martin Rasmussen; Alexei Veneziani

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We study coupling functions that allow for persistent synchronization in connected complex networks and any isolated system dynamics that possesses global solutions and bounded Jacobian evaluated along such solutions. We prove that the set of coupling functions leading to stable synchronization is open and that any coupling function whose linear part has eigenvalues with positive real part leads to system towards synchronization.

Source: http://arxiv.org/abs/1304.7679v1

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Sep 19, 2013
09/13

by
Alexei M. Veneziani; Tiago Pereira; Domingos H. U. Marchetti

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A remarkable property of Hermitian ensembles is their universal behavior, that is, once properly rescaled the eigenvalue statistics does not depend on particularities of the ensemble. Recently, normal matrix ensembles have attracted increasing attention, however, questions on universality for these ensembles still remain under debate. We analyze the universality properties of random normal ensembles. We show that the concept of universality used for Hermitian ensembles cannot be directly...

Source: http://arxiv.org/abs/0909.3418v1

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Sep 19, 2013
09/13

by
Alexei M. Veneziani; Tiago Pereira; Domingos H. U. Marchetti

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We investigate the eigenvalues statistics of ensembles of normal random matrices when their order N tends to infinite. In the model the eigenvalues have uniform density within a region determined by a simple analytic polynomial curve. We study the conformal deformations of normal random ensembles to Hermitian random ensembles and give sufficient conditions for the latter to be a Wigner ensemble.

Source: http://arxiv.org/abs/0909.0978v1

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32

Sep 21, 2013
09/13

by
Alexei M. Veneziani; Tiago Pereira; Domingos H. U. Marchetti

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We use the steepest descents method to study the integral kernel of a family of normal random matrix ensembles with eigenvalue distribution P_{N}(z_{1},...,z_{N}) = Z_{N}^{-1} e^{-N\Sigma_{i=1}^{N}V_{\alpha}(z_{i})} \Pi_{1\leqi

Source: http://arxiv.org/abs/1106.4858v1

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2.0

Jun 28, 2018
06/18

by
Daniel M. N. Maia; Tiago Pereira; Elbert E. N. Macau

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We investigate the persistence of synchronization in networks of diffusively coupled oscillators when the coupling functions are nonidentical. Under mild conditions, we uncover the influence of the network interaction structure on the mismatches of the coupling function. We show that Erd\"os-R\'enyi random graphs support large perturbations in the coupling function. In contrast scale-free graphs do not allow large perturbations in the coupling function, that is, as the network size n goes...

Topics: Dynamical Systems, Mathematics

Source: http://arxiv.org/abs/1511.08065

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2.0

Jun 30, 2018
06/18

by
Yong Zou; Tiago Pereira; Michael Small; Zonghua Liu; Jürgen Kurths

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Spontaneous explosive emergent behavior takes place in heterogeneous networks when the frequencies of the nodes are positively correlated to the node degree. A central feature of such explosive transitions is a hysteretic behavior at the transition to synchronization. We unravel the underlying mechanisms and show that the dynamical origin of the hysteresis is a change of basin of attraction of the synchronization state. Our findings hold for heterogeneous networks with star graph motifs such as...

Topics: Nonlinear Sciences, Chaotic Dynamics

Source: http://arxiv.org/abs/1401.1262

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Sep 22, 2013
09/13

by
Tiago Pereira; Deniz Eroglu; G. B. Bagci; U. Tirnakli; Henrik J. Jensen

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We study the emergence of coherence in complex networks of mutually coupled non-identical elements. We uncover the precise dependence of the dynamical coherence on the network connectivity, on the isolated dynamics of the elements and the coupling function. These findings predict that in random graphs, the enhancement of coherence is proportional to the mean degree. In locally connected networks, coherence is no longer controlled by the mean degree, but rather on how the mean degree scales with...

Source: http://arxiv.org/abs/1302.3137v2

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Sep 21, 2013
09/13

by
Dan Kiselman; Tiago Pereira; Bengt Gustafsson; Martin Asplund; Jorge Meléndez; Kai Langhans

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Context: In studies of the solar spectrum relative to spectra of solar twin stars, it has been found that the chemical composition of the Sun seems to depart systematically from those of the twins. One possible explanation is that the effect is due to the special aspect angle of the Sun when observed from Earth, as compared with the aspect angles of the twins. Thus, a latitude dependence of the solar spectrum, even with the heliocentric angle constant, could lead to effects of the type...

Source: http://arxiv.org/abs/1108.4527v2

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Oct 26, 2014
10/14

by
SILVA, Emmanuel Joao Nogueira Leal; HERRERA, Daniel Rodrigo; ROSA, Tiago Pereira; DUQUE, Thais Mageste; JACINTO, Rogerio Castilho; GOMES, Brenda Paula Figueiredo de Almeida; ZAIA, Alexandre Augusto

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This article is from Journal of Applied Oral Science , volume 22 . Abstract A calcium aluminate-based endodontic material, EndoBinder, has been developed in order to reduce MTA negative characteristics, preserving its biological properties and clinical applications. Objectives: The aim of this study was to evaluate the cytotoxicity, antimicrobial activity, pH, solubility and water sorption of EndoBinder and to compare them with those of white MTA (WMTA). Material and Methods: Cytotoxicity was...

Source: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3908766