254 research outputs found
Coevolution of dynamical states and interactions in dynamic networks
We explore the coupled dynamics of the internal states of a set of
interacting elements and the network of interactions among them. Interactions
are modeled by a spatial game and the network of interaction links evolves
adapting to the outcome of the game. As an example we consider a model of
cooperation, where the adaptation is shown to facilitate the formation of a
hierarchical interaction network that sustains a highly cooperative stationary
state. The resulting network has the characteristics of a small world network
when a mechanism of local neighbor selection is introduced in the adaptive
network dynamics. The highly connected nodes in the hierarchical structure of
the network play a leading role in the stability of the network. Perturbations
acting on the state of these special nodes trigger global avalanches leading to
complete network reorganization.Comment: 4 pages, 5 figures, for related material visit
http:www.imedea.uib.es/physdept
Cooperation and the Emergence of Role Differentiation in the Dynamics of Social Networks
By means of extensive computer simulations, the authors consider the
entangled coevolution of actions and social structure in a new version of a
spatial Prisoner's Dilemma model that naturally gives way to a process of
social differentiation. Diverse social roles emerge from the dynamics of the
system: leaders are individuals getting a large payoff who are imitated by a
considerable fraction of the population, conformists are unsatisfied
cooperative agents that keep cooperating, and exploiters are defectors with a
payoff larger than the average one obtained by cooperators. The dynamics
generate a social network that can have the topology of a small world network.
The network has a strong hierarchical structure in which the leaders play an
essential role in sustaining a highly cooperative stable regime. But
disruptions affecting leaders produce social crises described as dynamical
cascades that propagate through the network.Comment: (15 pages, 7 figures
Forecasting the SST space-time variability of the Alboran Sea with genetic algorithms
We propose a nonlinear ocean forecasting technique based on a combination of
genetic algorithms and empirical orthogonal function (EOF) analysis. The method
is used to forecast the space-time variability of the sea surface temperature
(SST) in the Alboran Sea. The genetic algorithm finds the equations that best
describe the behaviour of the different temporal amplitude functions in the EOF
decomposition and, therefore, enables global forecasting of the future
time-variability.Comment: 15 pages, 3 figures; latex compiled with agums.st
Operation Allelopathy: An Experiment Investigating an Alternative to Synthetic Agrochemicals
Synthetic herbicides represent a serious problem in modern agriculture because they are not biodegradable and can accumulate in the soil and in the groundwater, a situation that allows them to enter the trophic chain and ultimately leads to human exposure. Allelopathic chemicals offer an effective alternative to the synthetic compounds. The aim of this experiment is to highlight the differences between chemical and biological control of diseases in crops and to demonstrate the use of natural fungicides and herbicides as alternatives to synthetic chemicals. The experiment involves an evaluation by students of the potential of plant extracts as an alternative to synthetic agrochemicals to identify new ecological farming techniques that could be applied in agriculture. In an effort to encourage 1800 students in high school (14 to 16 years old) to have an interest in science, technology, and innovation, the third edition of the Summer Science Campus was organized by the Spanish Foundation for Science and Technology and the Ministry of Education, Culture, and Sports with support from the foundation Obra Social “la Caixa”
BRS symmetry restoration of chiral Abelian Higgs-Kibble theory in dimensional renormalization with a non-anticommuting
The one-loop renormalization of the abelian Higgs-Kibble model in a general
't Hooft gauge and with chiral fermions is fully worked out within dimensional
renormalization scheme with a non-anticommuting . The anomalous terms
introduced in the Slavnov-Taylor identities by the minimal subtraction
algorithm are calculated and the asymmetric counterterms needed to restore the
BRS symmetry, if the anomaly cancellation conditions are met, are computed. The
computations draw heavily from regularized action principles and Algebraic
Renormalization theory.Comment: 32 pages, 11 figures, one table, plane tex in several files, uses
epsf.tex. Mathematica programs which generate the tex files with results are
included. V.2: references added and minor typos correcte
Measurement of the cosmic ray spectrum above eV using inclined events detected with the Pierre Auger Observatory
A measurement of the cosmic-ray spectrum for energies exceeding
eV is presented, which is based on the analysis of showers
with zenith angles greater than detected with the Pierre Auger
Observatory between 1 January 2004 and 31 December 2013. The measured spectrum
confirms a flux suppression at the highest energies. Above
eV, the "ankle", the flux can be described by a power law with
index followed by
a smooth suppression region. For the energy () at which the
spectral flux has fallen to one-half of its extrapolated value in the absence
of suppression, we find
eV.Comment: Replaced with published version. Added journal reference and DO
Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory
The Auger Engineering Radio Array (AERA) is part of the Pierre Auger
Observatory and is used to detect the radio emission of cosmic-ray air showers.
These observations are compared to the data of the surface detector stations of
the Observatory, which provide well-calibrated information on the cosmic-ray
energies and arrival directions. The response of the radio stations in the 30
to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of
the incoming electric field. For the latter, the energy deposit per area is
determined from the radio pulses at each observer position and is interpolated
using a two-dimensional function that takes into account signal asymmetries due
to interference between the geomagnetic and charge-excess emission components.
The spatial integral over the signal distribution gives a direct measurement of
the energy transferred from the primary cosmic ray into radio emission in the
AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air
shower arriving perpendicularly to the geomagnetic field. This radiation energy
-- corrected for geometrical effects -- is used as a cosmic-ray energy
estimator. Performing an absolute energy calibration against the
surface-detector information, we observe that this radio-energy estimator
scales quadratically with the cosmic-ray energy as expected for coherent
emission. We find an energy resolution of the radio reconstruction of 22% for
the data set and 17% for a high-quality subset containing only events with at
least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO
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