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 $V_p$. 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 $V_L$ of infinitesimal errors. If linear mechanisms prevail on the nonlinear ones $V_p = V_L$. On the contrary, if nonlinear effects are predominant finite amplitude disturbances can eventually propagate faster than infinitesimal ones (i.e. $V_p > V_L$). 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 $V_p$ 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 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

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