2,523 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
What is the temperature of a granular medium?
In this paper we discuss whether thermodynamical concepts and in particular
the notion of temperature could be relevant for the dynamics of granular
systems. We briefly review how a temperature-like quantity can be defined and
measured in granular media in very different regimes, namely the glassy-like,
the liquid-like and the granular gas. The common denominator will be given by
the Fluctuation-Dissipation Theorem, whose validity is explored by means of
both numerical and experimental techniques. It turns out that, although a
definition of a temperature is possible in all cases, its interpretation is far
from being obvious. We discuss the possible perspectives both from the
theoretical and, more importantly, from the experimental point of view
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
Modeling the emergence of universality in color naming patterns
The empirical evidence that human color categorization exhibits some
universal patterns beyond superficial discrepancies across different cultures
is a major breakthrough in cognitive science. As observed in the World Color
Survey (WCS), indeed, any two groups of individuals develop quite different
categorization patterns, but some universal properties can be identified by a
statistical analysis over a large number of populations. Here, we reproduce the
WCS in a numerical model in which different populations develop independently
their own categorization systems by playing elementary language games. We find
that a simple perceptual constraint shared by all humans, namely the human Just
Noticeable Difference (JND), is sufficient to trigger the emergence of
universal patterns that unconstrained cultural interaction fails to produce. We
test the results of our experiment against real data by performing the same
statistical analysis proposed to quantify the universal tendencies shown in the
WCS [Kay P and Regier T. (2003) Proc. Natl. Acad. Sci. USA 100: 9085-9089], and
obtain an excellent quantitative agreement. This work confirms that synthetic
modeling has nowadays reached the maturity to contribute significantly to the
ongoing debate in cognitive science.Comment: Supplementery Information available here
http://www.pnas.org/content/107/6/2403/suppl/DCSupplementa
Distance Education: Exploring Trends and Issues in the Global Context
With the end goal of informing school management practices, this paper presents a comprehensive review of literature and studies on the trends and issues of Distance Education (DE) in the global context. Due to the development of communication technologies, the change in the modes of Distance Education is very abrupt. Internationalization, cost-effectiveness, access, infrastructure, and quality are some of the trends being faced by our contemporary education system. However, the literature and research findings also revealed that there are some emerging issues in the field such as dropout rates, assessment of students, student concerns, cost-effectiveness, issues related to technology use, and infrastructure. Keywords: Distance Education, trends, issues, e-learning, education, Open University DOI: 10.7176/JEP/11-4-15 Publication date: February 29th 202
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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Bootstrapping communication in language games
Semiotic dynamics is a fast growing field according to which language can be seen as an evolving and self-organizing system. In this paper we present a simple multi-agent framework able to account for the emergence of shared conventions in a population. Agents perform pairwise games and final consensus is reached without any outside control nor any global knowledge of the system. In particular we discuss how embedding the population in a non trivial interaction topology affects the behavior of the system and forces to carefully consider agents selection strategies. These results cast an interesting framework to address and study more complex issues in semiotic dynamics
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On the origin of universal categorization patterns: an in-silica experiment
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