Casimir Energy and Entropy in the Sphere--Sphere Geometry

We calculate the Casimir energy and entropy for two spheres described by the perfect metal model, plasma model, and Drude model in the large separation limit. We obtain nonmonotonic behavior of the Helmholtz free energy with separation and temperature for the perfect metal and plasma models, leading to parameter ranges with negative entropy, and also nonmonotonic behavior of the entropy with temperature and the separation between the spheres. This nonmonotonic behavior has not been found for Drude model. The appearance of this anomalous behavior of the entropy is discussed as well as its thermodynamic consequences.Comment: 9 pages, 7 figure

Relativistic Quantum Optics: On the relativistic invariance of the light-matter interaction models

In this note we discuss the invariance under general changes of reference frame of all the physical predictions of particle detector models in quantum field theory in general and, in particular, of those used in quantum optics to model atoms interacting with light. We find explicitly how the light-matter interaction Hamiltonians change under general coordinate transformations, and analyze the subtleties of the Hamiltonians commonly used to describe the light-matter interaction when relativistic motion is taken into account.Comment: 11 pages. ReVteX 4.1. V2: Updated to match published versio

The Regional Policy of the European Union and the Enlargement Process to Central and Eastern European Countries

The successive enlargement processes of the European Union have implied reforms in Regional Policy. Since the Single European Act (1987), Europe has got a structural policy mainly focused on regions whose development is lagging behind. The accession of CEECs will mean an extraordinary increase in regional development disparities. However, the current EU Regional Policy is addressed to deal with such a kind of development lags. Competition in a large market combined with regional development policy of the EU is a successful policy mix to boost growth of CEECs in the framework of an open market economy. The own success of regional policy in current objective 1 regions will led to an important reduction of assisted population. The financial perspectives approved in the Berlin Summit (March 1999) provides enough financial space to assist 90% of population in CEECs and 75% of current population under objective 1. The main challenge involved in the successful extension of EU Regional Policy to CEECs lies in the field of management capabilities and administration reforms that must be carried out in these countries.Regional Policy, European Union, Central and Eastern European Countries

How tight should one's hands be tied? Fear of floating and credibility of exchange rate regimes

This paper analyzes the linkages between the credibility of a target zone regime, the volatility of the exchange rate, and the width of the band where the exchange rate is allowed to fluctuate. These three concepts should be related since the band width induces a trade-off between credibility and volatility. Narrower bands should give less scope for the exchange rate to fluctuate but may make agents perceive a larger probability of realignment which by itself should increase the volatility of the exchange rate. We build a model where this trade-off is made explicit. The model is used to understand the reduction in volatility experienced by most EMS countries after their target zones were widened on August 1993. As a natural extension, the model also rationalizes the existence of non-official, implicit target zones (or fear of floating), suggested by some authors.fear of floating, target zones, exchange rate arrangements, rational expectations, credibility

Regional Policy and Convergence in Europe: The Case of Backward Regions

This paper analyzes the performance of regions whose development is lagging behind since the institutionalization of the EU regional policy, (1989). Results from a panel data model with fixed effects prove that backward regions have been catching up with the EU average income since the launching of the first programming period, the so called Delors'I package, 1989-1993

Theory of the Strain-Induced Magnetoelectric Effect in Planar Dirac Systems

The magnetoelectric response in inversion-breaking two dimensional Dirac systems induced by strain is analyzed. It is shown that, in the same way that the piezoelectric response in these materials is related to the valley Chern number, the strain-induced magnetoelectric effect is related both to the non trivial Berry curvature and the derivative of the orbital magnetic moment per valley. This phenomenon allows to locally induce and control charge densities by an external magnetic field in strained zones of the sample.Comment: 7 pages, 2 figure

The tidally disturbed luminous compact blue galaxy Mkn 1087 and its surroundings

We present new broad-band optical and near-infrared CCD imaging together with deep optical intermediate-resolution spectroscopy of Mkn 1087 and its surrounding objects. We analyze the morphology and colors of the stellar populations of the brightest objects, some of them star-formation areas, as well as the kinematics, physical conditions and chemical composition of the ionized gas associated with them. Mkn 1087 does not host an Active Galactic Nucleus, but it could be a Luminous Compact Blue Galaxy. Although it was classified as a suspected Wolf-Rayet galaxy, we do not detect the spectral features of these sort of massive stars. Mkn 1087 shows morphological and kinematical features that can be explained assuming that it is in interaction with two nearby galaxies: the bright KPG 103a and a dwarf ($M_B\sim-18$) star-forming companion. We argue that this dwarf companion is not a tidal object but an external galaxy because of its low metallicity [12+log(O/H) = 8.24] with respect to the one derived for Mkn 1087 [12+log(O/H) = 8.57] and its kinematics. Some of the non-stellar objects surrounding Mkn 1087 are connected by bridges of matter with the main body, host star-formation events and show similar abundances despite their different angular distances. These facts, together their kinematics, suggest that they are tidal dwarf galaxies formed from material stripped from Mkn 1087. A bright star-forming region at the south of Mkn 1087 (knot #7) does not show indications of being a tidal galaxy or the product of a merging process as suggested in previous works. We argue that Mkn 1087 and its surroundings should be considered a group of galaxies.Comment: Accepted by A&A, 21 pages, 13 figures, 8 table

Regional Convergence in the European Union: Results from a Panel Data Model

This paper evaluates the convergence process for different samples of European Union regions during the period 1982-1999 by using fixed effects panel data regressions. This estimation method allows us to control for unobserved time-invariant heterogeneity in cross-sectional models. The results of growth rates are significantly negatively related to income levels and show that the convergence relationship holds. However when regions are bound to very different steady state positions, convergence to a common income level appears to be impossible.