The Atomic Lighthouse Effect

We investigate the deflection of light by a cold atomic cloud when the light-matter interaction is locally tuned via the Zeeman effect using magnetic field gradients. This "lighthouse" effect is strongest in the single-scattering regime, where deviation of the incident field is largest. For optically dense samples, the deviation is reduced by collective effects, as the increase in linewidth leads to a decrease of the magnetic field efficiency

The ground-state of General Relativity, Topological Theories and Dark Matter

We suggest a limit of Einstein equations incorporating the state $g_{\mu\nu}=0$ as a solution. The large scale behavior of this theory has interesting properties. For a spherical source, the velocity profile for circular motions is of the form observed in galaxies (approximately flat). For FRW cosmologies, the Friedman equation contains an additional contribution in the matter sector.Comment: More clarifications on the interpretation of the limits. Shorter version. 4 pages, two column, no figure

Attitudes toward immigrants: a cross-country perspective

This paper examines the foundations of attitudes towards immigrants by focusing on individual characteristics and country-specific effects. We use a micro-level data set from 31 countries. In particular, we utilize the module on National Identity of the 2003 International Social Survey Program (ISSP). Results indicate that gender, education, age, labor-market status, and political and religious affiliation are important indicators of the attitude toward immigrants. The largest effect appears to be that of education, with more education being positively correlated with a positive view of immigrants. Additionally, we find that country of residence matters.immigration, microeconomic behavior, comparative research.

A tensor instability in the Eddington inspired Born-Infeld Theory of Gravity

In this paper we consider an extension to Eddington's proposal for the gravitational action. We study tensor perturbations of a homogeneous and isotropic space-time in the Eddington regime, where modifications to Einstein gravity are strong. We find that the tensor mode is linearly unstable deep in the Eddington regime and discuss its cosmological implications.Comment: 5 pages, approved by Phys. Rev. D, additional references and minor modification

Health and happiness in Uruguay

This article presents a study of the relationship between self-reported happiness and selfassessed health status at the individual level, using the Religion, Health, and Young Emancipation ISSP survey for Uruguay in 2008. Probit estimates suggest that better selfassessed health status is highly correlated with greater levels of self-reported happiness. In order to control for the observed heterogeneity, models are estimated using matching methods. Results show that individuals who report themselves to be in good health have a probability of being at the highest level of happiness between 18 and 29 percentage points higher than individuals who report worse health.The authors thank the University of North Texas and the University of Pennsylvania for funding this study

A New Integrated Approach for Fast Intrinsic Dielectric Breakdown

FCT-MCTES Portugal through UID/EEA/00066/2013 is gratefully acknowledged.A non-equilibrium phenomenological description for a complete dielectric breakdown sequence in perfect solid electric insulators, from the dynamics of instability to the growth of branching patterns, is implemented. It represents an original treatment which allows overcoming the current lack of such a complete physical description, involving thermodynamics, and in particular equations on maximum dissipation energy for dielectric breakdown are developed. From the assumption that there is a time delay in the energy rates and propagation speeds between the system input and output, a principle of maximum energy dissipation is postulated and corresponding dynamic evolution equations were obtained. It is shown that the delay in those speeds gives rise to the appearance of iterated equations which in turn leads to the logistic maps describing the dynamic evolution of the system. The results can describe the instability process along with dissipation patterns formation. The vast theoretical and experimental analogies between mechanical fracture and dielectric rupture, lead us to foresee the potential applicability of this model in the prediction of dielectric rupture patterns. This work opens then the possibility to predict the consequent branching patterns by using a maximum energy dissipation principle, contributing in a significant way for energy efficiency engineering.publishersversionpublishe

Eddington-Born-Infeld action for dark energy and dark matter

We argue that Einstein gravity coupled to a Born-Infeld theory provides an attractive candidate to represent dark matter and dark energy. For cosmological models, the Born-Infeld field has an equation of state which interpolates between matter, w=0 (small times), and a cosmological constant w=-1 (large times). On galactic scales, the Born-Infeld field predicts asymptotically flat rotation curves.Comment: A sign mistake in section on galactic scales is pointed out. This sign invalidates the content of that section. See comment on manuscrip

El estado de salud de los jóvenes uruguayos

This paper is a study of the health of young people in Uruguay. The empirical work is based on the “Health and Social Networks” survey carried out by the Department of Economics of the Social Sciences Faculty, in agreement with the National Youth Institute, in 2004. Using an ordered probit, the probability of having very good, good, or bad health status is estimated, controlled by socio-economic factors and risk-linked behavior. It is found that the probability of having better health status depends positively on education, physical activity, not being undernourished, not smoking, living in small cities, having human capital and living in a household with less relative privation. In reference to health status and the economic status of the family, the first fifteen years of life appears as positively determining it. In order to identify groups at risk, several simulations are done, predicting probabilities for several groups such as: behavior that causes a serious health risk (smoking, drinking alcohol, not doing physical excursive, being undernourished or obese), people with low socio-economic status (living in a household with high relative privation, economic problems in the first fifteen years of life, falling behind in the education system and not having human capital), and both at the same time. It has been found that those with risk behavior have a 14 per cent probability of having very good health status (as against the average, which is 24 per cent), the figure for those with low socio-economic status is 4 per cent, and the figure for those with both characteristics just 2 per cent.health status, health production, human capital, youth