711 research outputs found
La crisis de la deuda soberana o pública: el caso de España
The sovereign debt crisis is often evoked as one of the main causes of the economic
difficulties faced by net importing countries and as the rationale behind the austerity measures
imposed on their residents. Nothing seems more evident than a country whose global,
commercial and financial, imports exceed its global exports has to finance its deficit through
a foreign loan. This inevitably leads to the formation of an external debt. Yet, things are less
straightforward than they might appear, and a rigorous analysis is called for to verify whether
any country’ sovereign debt is ever justifiable. The paper shows that it is because net global
imports are paid twice that net importing countries run up a sovereign debt. The case of Spain is
symptomatic and provides statistical confirmation of the pathological increase in the country’s
external debtLa crisis de la deuda soberana suele considerarse como una de las principales causas
de las dificultades económicas a las que se enfrentan los países importadores netos. Constituye
asimismo la razón que justifica las medidas de austeridad impuestas a sus residentes. Nada
parece más evidente que un país, cuyas importaciones globales, comerciales y financieras, exceden
sus exportaciones globales, tenga que financiar su déficit mediante un préstamo extranjero.
Lo que conduce inevitablemente a la formación de la deuda exterior. Sin embargo, la realidad
es más compleja de lo que parece. De ahí que sea necesario un análisis riguroso que aclare si
la deuda soberana de cada país está justificada. Este artículo muestra que no lo está, desde el
momento en que los países importadores netos se encuentran con una deuda soberana debido
al doble coste de las importaciones globales netas. El caso espa˜nol es sintomático y aporta
confirmación estadística del aumento patológico de la deuda exterior del paí
Linear and nonlinear information flow in spatially extended systems
Infinitesimal and finite amplitude error propagation in spatially extended
systems are numerically and theoretically investigated. The information
transport in these systems can be characterized in terms of the propagation
velocity of perturbations . A linear stability analysis is sufficient to
capture all the relevant aspects associated to propagation of infinitesimal
disturbances. In particular, this analysis gives the propagation velocity
of infinitesimal errors. If linear mechanisms prevail on the nonlinear ones
. On the contrary, if nonlinear effects are predominant finite
amplitude disturbances can eventually propagate faster than infinitesimal ones
(i.e. ). The finite size Lyapunov exponent can be successfully
employed to discriminate the linear or nonlinear origin of information flow. A
generalization of finite size Lyapunov exponent to a comoving reference frame
allows to state a marginal stability criterion able to provide both in
the linear and in the nonlinear case. Strong analogies are found between
information spreading and propagation of fronts connecting steady states in
reaction-diffusion systems. The analysis of the common characteristics of these
two phenomena leads to a better understanding of the role played by linear and
nonlinear mechanisms for the flow of information in spatially extended systems.Comment: 14 RevTeX pages with 13 eps figures, title/abstract changed minor
changes in the text accepted for publication on PR
Synchronization of extended chaotic systems with long-range interactions: an analogy to Levy-flight spreading of epidemics
Spatially extended chaotic systems with power-law decaying interactions are
considered. Two coupled replicas of such systems synchronize to a common
spatio-temporal chaotic state above a certain coupling strength. The
synchronization transition is studied as a nonequilibrium phase transition and
its critical properties are analyzed at varying the interaction range. The
transition is found to be always continuous, while the critical indexes vary
with continuity with the power law exponent characterizing the interaction.
Strong numerical evidences indicate that the transition belongs to the {\it
anomalous directed percolation} family of universality classes found for
L{\'e}vy-flight spreading of epidemic processes.Comment: 4 revTeX4.0 pages, 3 color figs;added references and minor
changes;Revised version accepted for pubblication on PR
Synchronization of spatio-temporal chaos as an absorbing phase transition: a study in 2+1 dimensions
The synchronization transition between two coupled replicas of
spatio-temporal chaotic systems in 2+1 dimensions is studied as a phase
transition into an absorbing state - the synchronized state. Confirming the
scenario drawn in 1+1 dimensional systems, the transition is found to belong to
two different universality classes - Multiplicative Noise (MN) and Directed
Percolation (DP) - depending on the linear or nonlinear character of damage
spreading occurring in the coupled systems. By comparing coupled map lattice
with two different stochastic models, accurate numerical estimates for MN in
2+1 dimensions are obtained. Finally, aiming to pave the way for future
experimental studies, slightly non-identical replicas have been considered. It
is shown that the presence of small differences between the dynamics of the two
replicas acts as an external field in the context of absorbing phase
transitions, and can be characterized in terms of a suitable critical exponent.Comment: Submitted to Journal of Statistical Mechanics: Theory and Experimen
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