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Search Results: 1 - 10 of 99 matches for " Motter "
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Bounding network spectra for network design
Adilson E. Motter
Physics , 2007, DOI: 10.1088/1367-2630/9/6/182
Abstract: The identification of the limiting factors in the dynamical behavior of complex systems is an important interdisciplinary problem which often can be traced to the spectral properties of an underlying network. By deriving a general relation between the eigenvalues of weighted and unweighted networks, here I show that for a wide class of networks the dynamical behavior is tightly bounded by few network parameters. This result provides rigorous conditions for the design of networks with predefined dynamical properties and for the structural control of physical processes in complex systems. The results are illustrated using synchronization phenomena as a model process.
Improved Network Performance via Antagonism: From Synthetic Rescues to Multi-drug Combinations
Adilson E. Motter
Physics , 2010, DOI: 10.1002/bies.200900128
Abstract: Recent research shows that a faulty or sub-optimally operating metabolic network can often be rescued by the targeted removal of enzyme-coding genes--the exact opposite of what traditional gene therapy would suggest. Predictions go as far as to assert that certain gene knockouts can restore the growth of otherwise nonviable gene-deficient cells. Many questions follow from this discovery: What are the underlying mechanisms? How generalizable is this effect? What are the potential applications? Here, I will approach these questions from the perspective of compensatory perturbations on networks. Relations will be drawn between such synthetic rescues and naturally occurring cascades of reaction inactivation, as well as their analogues in physical and other biological networks. I will specially discuss how rescue interactions can lead to the rational design of antagonistic drug combinations that select against resistance and how they can illuminate medical research on cancer, antibiotics, and metabolic diseases.
Spontaneous Synchrony Breaking
Adilson E. Motter
Physics , 2010, DOI: 10.1038/nphys1609
Abstract: Research on synchronization of coupled oscillators has helped explain how uniform behavior emerges in populations of non-uniform systems. But explaining how uniform populations engage in sustainable non-uniform synchronization may prove to be just as fascinating.
Relativistic chaos is coordinate invariant
Adilson E. Motter
Physics , 2003, DOI: 10.1103/PhysRevLett.91.231101
Abstract: The noninvariance of Lyapunov exponents in general relativity has led to the conclusion that chaos depends on the choice of the space-time coordinates. Strikingly, we uncover the transformation laws of Lyapunov exponents under general space-time transformations and we find that chaos, as characterized by positive Lyapunov exponents, is coordinate invariant. As a result, the previous conclusion regarding the noninvariance of chaos in cosmology, a major claim about chaos in general relativity, necessarily involves the violation of hypotheses required for a proper definition of the Lyapunov exponents.
Cascade control and defense in complex networks
Adilson E. Motter
Physics , 2004, DOI: 10.1103/PhysRevLett.93.098701
Abstract: Complex networks with heterogeneous distribution of loads may undergo a global cascade of overload failures when highly loaded nodes or edges are removed due to attacks or failures. Since a small attack or failure has the potential to trigger a global cascade, a fundamental question regards the possible strategies of defense to prevent the cascade from propagating through the entire network. Here we introduce and investigate a costless strategy of defense based on a selective further removal of nodes and edges, right after the initial attack or failure. This intentional removal of network elements is shown to drastically reduce the size of the cascade.
Adilson E. Motter
Mathematics , 2015, DOI: 10.1063/1.4931570
Abstract: An increasing number of complex systems are now modeled as networks of coupled dynamical entities. Nonlinearity and high-dimensionality are hallmarks of the dynamics of such networks but have generally been regarded as obstacles to control. Here I discuss recent advances on mathematical and computational approaches to control high-dimensional nonlinear network dynamics under general constraints on the admissible interventions. I also discuss the potential of network control to address pressing scientific problems in various disciplines.
Monocultura da eficiência capitalista
Adriana Fátima Canova Motter
Revista Espa?o Acadêmico , 2010,
Abstract: O presente artigo prop e uma análise do que o sociólogo português Boaventura Santos Souza considera como monoculturas que dominam o mundo, entre elas, a eficiência capitalista. Referem-se a formas de pensamento incutidas na racionalidade e práticas da sociedade moderna, de modo consciente ou inconsciente, resultado da pujante conduta da Modernidade no que se refere ao domínio sobre a natureza através das tecnologias e agu ada ambi o pelo lucro. Uma realidade de maior equidade poderá ser construída se tais monoculturas forem contestadas, comprometendo-se a construir novos paradigmas, diferentes dos atuais, os quais resgatem valores e princípios centrais de nossa condi o como seres humanos inseridos no contexto de um planeta de capacidade limitada. Assim, podemos acreditar que é possível construir um desenvolvimento verdadeiramente sustentável. ABSTRACT This article proposes an analysis of the Portuguese sociologist Boaventura Souza Santos considers as monocultures that dominate the world, including the capitalist efficiency. Refer to ways of thinking instilled in rationality and practices of modern society, consciously or unconsciously, the result of vigorous conduct of modernity with regard to control over nature through technology and keen lust for profit. A reality of greater equity can be built if these plantations are in dispute, pledging to build new paradigms, different than today, which rescue values and core principles of our condition as human beings within the context of a planet of limited capacity. Thus, we believe that it is possible to build a truly sustainable development.
Time-metric equivalence and dimension change under time reparameterizations
Adilson E. Motter,Katrin Gelfert
Physics , 2009, DOI: 10.1103/PhysRevE.79.065202
Abstract: We study the behavior of dynamical systems under time reparameterizations, which is important not only to characterize chaos in relativistic systems but also to probe the invariance of dynamical quantities. We first show that time transformations are locally equivalent to metric transformations, a result that leads to a transformation rule for all Lyapunov exponents on arbitrary Riemannian phase spaces. We then show that time transformations preserve the spectrum of generalized dimensions D_q except for the information dimension D_1, which, interestingly, transforms in a nontrivial way despite previous assertions of invariance. The discontinuous behavior at q=1 can be used to constrain and extend the formulation of the Kaplan-Yorke conjecture.
Optimization in Networks
Adilson E. Motter,Zoltan Toroczkai
Physics , 2007, DOI: 10.1063/1.2751266
Abstract: The recent surge in the network modeling of complex systems has set the stage for a new era in the study of fundamental and applied aspects of optimization in collective behavior. This Focus Issue presents an extended view of the state of the art in this field and includes articles from a large variety of domains where optimization manifests itself, including physical, biological, social, and technological networked systems.
Discovering Network Structure Beyond Communities
Takashi Nishikawa,Adilson E. Motter
Physics , 2011, DOI: 10.1038/srep00151
Abstract: To understand the formation, evolution, and function of complex systems, it is crucial to understand the internal organization of their interaction networks. Partly due to the impossibility of visualizing large complex networks, resolving network structure remains a challenging problem. Here we overcome this difficulty by combining the visual pattern recognition ability of humans with the high processing speed of computers to develop an exploratory method for discovering groups of nodes characterized by common network properties, including but not limited to communities of densely connected nodes. Without any prior information about the nature of the groups, the method simultaneously identifies the number of groups, the group assignment, and the properties that define these groups. The results of applying our method to real networks suggest the possibility that most group structures lurk undiscovered in the fast-growing inventory of social, biological, and technological networks of scientific interest.
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