2,118 research outputs found
On the concept of complexity in random dynamical systems
We introduce a measure of complexity in terms of the average number of bits
per time unit necessary to specify the sequence generated by the system. In
random dynamical system, this indicator coincides with the rate K of divergence
of nearby trajectories evolving under two different noise realizations.
The meaning of K is discussed in the context of the information theory, and
it is shown that it can be determined from real experimental data. In presence
of strong dynamical intermittency, the value of K is very different from the
standard Lyapunov exponent computed considering two nearby trajectories
evolving under the same randomness. However, the former is much more relevant
than the latter from a physical point of view as illustrated by some numerical
computations for noisy maps and sandpile models.Comment: 35 pages, LaTe
The Effects of Vouchers on Academic Achievement: Evidence from Chile’s Conditional Voucher Program Juan A. Correa David Inostroza Francisco Parro Loreto Reyes Gabriel Ugarte Universidad Andrés Bello Marzo
Indexación: UNAB
JEL Classi cation: H4; I2Abstract
We use data from Chile's conditional voucher program to test the e ects of vouchers
on academic achievement. Conditional vouchers have delivered extra resources
to low-income, vulnerable students since 2008. Moreover, under this scheme, additional
resources are contingent on the completion of speci c scholastic goals. Using a
di erence-in-di erences approach, we nd a positive and signi cant e ect of vouchers
on standardized test scores. Additionally, our results highlight the importance of
conditioning the delivery of resources to some speci c academic goals when frictions
exist in the education market
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Granulomatous fasciitis followed by morphea profunda: Is granulomatous fasciitis part of a spectrum of deep morphea? A case report and review of the literature.
Although eosinophilic fasciitis is known to be part of the deep morphea spectrum, this first report of the coexistence of granulomatous fasciitis and morphea profunda suggests that granulomatous fasciitis may also be a part of the spectrum of deep morphea
Characterization of chaos in random maps
We discuss the characterization of chaotic behaviours in random maps both in
terms of the Lyapunov exponent and of the spectral properties of the
Perron-Frobenius operator. In particular, we study a logistic map where the
control parameter is extracted at random at each time step by considering
finite dimensional approximation of the Perron-Frobenius operatorComment: Plane TeX file, 15 pages, and 5 figures available under request to
[email protected]
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On the origin of universal categorization patterns: an in-silica experiment
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Agreement dynamics on interaction networks with diverse topologies
We review the behavior of a recently introduced model of agreement dynamics, called the "Naming Game." This model describes the self-organized emergence of linguistic conventions and the establishment of simple communication systems in a population of agents with pairwise local interactions. The mechanisms of convergence towards agreement strongly depend on the network of possible interactions between the agents. In particular, the mean-field case in which all agents communicate with all the others is not efficient, since a large temporary memory is requested for the agents. On the other hand, regular lattice topologies lead to a fast local convergence but to a slow global dynamics similar to coarsening phenomena. The embedding of the agents in a small-world network represents an interesting tradeoff: a local consensus is easily reached, while the long-range links allow to bypass coarsening-like convergence. We also consider alternative adaptive strategies which can lead to faster global convergence
Exploring the roles of complex networks in linguistic categorization
This article adopts the category game model, which simulates the origins and evolution of linguistic categories in a group of artificial agents, to evaluate the effect of social structure on linguistic categorization. Based on the simulation results in a number of typical networks, we examine the isolating and collective effects of some structural features, including average degree, shortcuts, and level of centrality, on the categorization process. This study extends the previous simulations mainly on lexical evolution, and illustrates a general framework to systematically explore the effect of social structure on language evolution. © 2011 Massachusetts Institute of Technology.published_or_final_versio
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A fast no-rejection algorithm for the Category Game
The Category Game is a multi-agent model that accounts for the emergence of shared categorization patterns in a population of interacting individuals. In the framework of the model, linguistic categories appear as long lived consensus states that are constantly reshaped and re-negotiated by the communicating individuals. It is therefore crucial to investigate the long time behavior to gain a clear understanding of the dynamics. However, it turns out that the evolution of the emerging category system is so slow, already for small populations, that such an analysis has remained so far impossible. Here, we introduce a fast no-rejection algorithm for the Category Game that disentangles the physical simulation time from the CPU time, thus opening the way for thorough analysis of the model. We verify that the new algorithm is equivalent to the old one in terms of the emerging phenomenology and we quantify the CPU performances of the two algorithms, pointing out the neat advantages offered by the no-rejection one. This technical advance has already opened the way to new investigations of the model, thus helping to shed light on the fundamental issue of categorization
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