Theory of anomalous collective diffusion in colloidal monolayers on a spherical interface

A planar colloidal monolayer exhibits anomalous collective diffusion due to the hydrodynamic interactions. We investigate how this behavior is affected by the curvature of the monolayer when it resides on the interface of a spherical droplet. It is found that the characteristic times of the dynamics still exhibit the same anomalous scaling as in the planar case. The spatial distribution, however, shows a difference due to the relevance of the radius of the droplet. Since for the droplet this is both a global magnitude, i.e., pertaining the spatial extent of the spherical surface, and a local one, i.e., the radius of curvature, the question remains open as to which of these two features actually dominates in the case of a generically curved interface.Comment: 7 pages, 2 figure

The Trouble with Identity and Progressive Origins in Defending Labour Law

Debate about labour regulation is not new. What is new is the urgency with which labour law reform is promoted as an important fix to economic woes. In recent years, calls for reform resound in poor and rich countries alike. The economic crisis in the United States and in Europe has intensified these debates, making labour regulation a prime target for reform. In several US states public sector unions have been under attack, depicted as a privileged class that drains public funds with high wages, cosy benefits, and retirement privileges that no other workers enjoy. Several European countries have introduced austerity measures that target labour regulation and other foundations of the welfare state as sources of economic waste that they can no longer afford. Moreover, it is argued that “rigid” labour regulation hampers job creation, which can be strengthened through a program of labour flexibilisation

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

Scaling in the Timing of Extreme Events

Extreme events can come either from point processes, when the size or energy of the events is above a certain threshold, or from time series, when the intensity of a signal surpasses a threshold value. We are particularly concerned by the time between these extreme events, called respectively waiting time and quiet time. If the thresholds are high enough it is possible to justify the existence of scaling laws for the probability distribution of the times as a function of the threshold value, although the scaling functions are different in each case. For point processes, in addition to the trivial Poisson process, one can obtain double-power-law distributions with no finite mean value. This is justified in the context of renormalization-group transformations, where such distributions arise as limiting distributions after iterations of the transformation. Clear connections with the generalized central limit theorem are established from here. The non-existence of finite moments leads to a semi-parametric scaling law in terms of the sample mean waiting time, in which the (usually unkown) scale parameter is eliminated but not the exponents. In the case of time series, scaling can arise by considering random-walk-like signals with absorbing boundaries, resulting in distributions with a power-law "bulk" and a faster decay for long times. For large thresholds the moments of the quiet-time distribution show a power-law dependence with the scale parameter, and isolation of the latter and of the exponents leads to a non-parametric scaling law in terms only of the moments of the distribution. Conclusions about the projections of changes in the occurrence of natural hazards lead to the necessity of distinguishing the behavior of the mean of the distribution with the behavior of the extreme events.Comment: Submitted to a Chaos, Solitons and Fractals special issue on Extreme Event

Preliminary results of the AMIGA engineering array at the Pierre Auger Observatory

The Auger Muons and Infill for the Ground Array (AMIGA) aims to both extend the detection range of the Pierre Auger Observatory down to energies $\sim 10^{16.5}~\mathrm{eV}$ and to measure the muon content of extensive air showers. To accomplish these goals, its detection system is composed of an array of coupled water-Cherenkov and scintillation detectors deployed in a graded triangular grid of 433 and 750\,m spacings. At each position, the scintillation detector is buried $2.3~\mathrm{m}$ deep so as to shield it from the air shower electromagnetic component and thus only measure the muon component. These muon detectors have $30~\mathrm{m^2}$ area split into modules, each of them highly segmented in 64 plastic-scintillator strips with an embedded wavelength-shifter optical fiber to transport light to an optical sensor located at the center of the module. During the engineering array phase (finished in November 2017) two module areas ($5~\mathrm{m^2}$ and $10~\mathrm{m^2}$) and two optical sensors (photo-multiplier tubes and silicon-photomultipliers) were tested. In this work, we present the final performance of the muon detectors equipped with silicon-photomultipliers which were thereafter selected as the baseline design for the AMIGA production phase. Analyses and results are based both on laboratory and field measurements.Comment: Proceeding of the UHECR 2018 conference, submitted to the forthcoming EPJ Web of Conference