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Homogeneous and isotropic, nonsingular, bouncing world models are designed to evade the initial singularity at the beginning of the cosmic expansion. Here, we study the thermodynamics of the subset of these models governed by general relativity. Considering the entropy of matter, radiation and that the entropy of the apparent horizon is proportional to its area, we argue that these models do not respect the generalised second law of thermodynamics, also away from the bounce., 12 pages, 3 figures. Version published in the European Physical Journal C

An interesting approach to the cosmological coincidence problem is to allow dark matter and dark energy interact with each other also nongravitationally. We consider two general Ans\"{a}tze for such an interaction and appraise their ability to address the coincidence problem. We determine the average accuracy required on the cosmic expansion rate data to distinguish interacting cosmological models from the conventional $\Lambda$CDM scenario. We find that among the planned surveys the Wide Field Infrared Survey Telescope has the best chance to detect an interaction, though at a low significance level. To unambiguously determine the existence of an interaction one must, therefore, combine the said expansion data with other probes., Comment: 10 pages

A phenomenological attempt at alleviating the so-called coincidence problem is to allow the dark matter and dark energy to interact. By assuming a coupled quintessence scenario characterized by an interaction parameter $\epsilon$, we investigate the precision in the measurements of the expansion rate $H(z)$ required by future experiments in order to detect a possible deviation from the standard $\Lambda$CDM model ($\epsilon = 0$). We perform our analyses at two levels, namely: through Monte Carlo simulations based on $\epsilon$CDM models, in which $H(z)$ samples with different accuracies are generated and through an analytic method that calculates the error propagation of $\epsilon$ as a function of the error in $H(z)$. We show that our analytical approach traces simulations accurately and find that to detect an interaction {using $H(z)$ data only, these must reach an accuracy better than 1%., Comment: 4 pages, 3 figures, LaTeX

The second law of thermodynamics, in the presence of gravity, is known to hold at small scales, as in the case of black holes and self-gravitating radiation spheres. Using the Friedmann–Lemaitre–Robertson–Walker metric and the history of the Hubble factor, we argue that this law also holds at cosmological scales. Based on this, we study the connection between the deceleration parameter and the spatial curvature of the metric, Ω k , and set limits on the latter, valid for any homogeneous and isotropic cosmological model. Likewise, we devise strategies to determine the sign of the spatial curvature index k. Finally, assuming the lambda cold dark matter model is correct, we find that the acceleration of the cosmic expansion is increasing today.

The modeling and analysis generic interface for external numerical codes (MAGIX) is a model optimizer developed under the framework of the coherent set of astrophysical tools for spectroscopy (CATS) project. The MAGIX package provides a framework of an easy interface between existing codes and an iterating engine that attempts to minimize deviations of the model results from available observational data, constraining the values of the model parameters and providing corresponding error estimates. Many models (and, in principle, not only astrophysical models) can be plugged into MAGIX to explore their parameter space and find the set of parameter values that best fits observational/experimental data. MAGIX complies with the data structures and reduction tools of ALMA (Atacama Large Millimeter Array), but can be used with other astronomical and with non-astronomical data., 12 pages, 15 figures, 2 tables, paper is also available at http://www.aanda.org/articles/aa/pdf/forth/aa20063-12.pdf

Simple models of gravitational arcs are crucial to simulate large samples of these objects with full control of the input parameters. These models also provide crude and automated estimates of the shape and structure of the arcs, which are necessary when trying to detect and characterize these objects on massive wide area imaging surveys. We here present and explore the ArcEllipse, a simple prescription to create objects with shape similar to gravitational arcs. We also present PaintArcs, which is a code that couples this geometrical form with a brightness distribution and adds the resulting object to images. Finally, we introduce ArcFitting, which is a tool that fits ArcEllipses to images of real gravitational arcs. We validate this fitting technique using simulated arcs and apply it to CFHTLS and HST images of tangential arcs around clusters of galaxies. Our simple ArcEllipse model for the arc, associated to a S\'ersic profile for the source, recovers the total signal in real images typically within 10%-30%. The ArcEllipse+S\'ersic models also automatically recover visual estimates of length-to-width ratios of real arcs. Residual maps between data and model images reveal the incidence of arc substructure. They may thus be used as a diagnostic for arcs formed by the merging of multiple images. The incidence of these substructures is the main factor preventing ArcEllipse models from accurately describing real lensed systems., Comment: 12 pages, 11 figures, accepted for publication in A&A

Brazil is not prepared to cope with population ageing. In fact, the country already spends a high proportion of GDP on retirement benefits given its income level and its still relatively young population. As a consequence, the deficit of the social security system has steadily increased since 1996 and is already approaching 6% of the Brazilian GDP. Several explanations have been provided for this increase such as the generous pensions provided mainly for civil servants whose benefits do not have an upper limit, the lack of a statutory minimum retirement age for those who contribute to the system for a certain period of time, the widespread labor informality which undermines the capability of the system to increase its revenue. Even though some attempts to reform the social security since the 1990s, there is a lot to be done in order to bring the trajectory of deficit back on track. In this paper, we develop, estimate and calibrate a dynamic general equilibrium model of occupational choice and retirement behavior to quantitatively study the social security problem in Brazil. In particular, in our model economy agents choose whether to work in the public, formal or informal sectors or stay home and, at later stages of the life-cycle, they are also allowed to decide the age of retirement. We estimate the parameters of the model by matching data moments on occupational choices, employment transitions, wages, and retirement from the Brazilian Monthly Employment Survey (Pesquisa Mensal de Emprego). Several counterfactual experiments are carried out in order to assess how changes in the rules of the social security affect labor allocation across the sectors, retirement behavior and life-cycle savings.

RESUMO Este artigo utiliza a estrutura da Teoria do Crescimento Endógeno para examinar as perspectivas de longo prazo da economia brasileira. Estudamos o comportamento dessas variáveis identificadas pela teoria como centrais para o desenvolvimento. O artigo argumenta que o desempenho do sistema educacional brasileiro é ruim, mesmo para os padrões da América Latina. Ainda existem muitas restrições de mercado e outras barreiras ao comércio e à adoção de tecnologia. Os serviços e investimentos em infraestrutura são deficientes e o sistema tributário muito concentrado e distorcido. Portanto, embora esses fatores persistam, não é provável que o país cresça a taxas sustentáveis comparáveis às experimentadas duas décadas atrás. No entanto, a privatização dos setores de infraestrutura pode estimular um boom temporário à medida que o investimento aumenta para satisfazer a demanda reprimida. ABSTRACT This article uses Endogenous Growth Theory framework to examine long term prospects of Brazilian economy. We study the behavior of those variables identified by theory as central for development. The article argues that Brazil’s educational system performance is poor even by Latin America standards. There are still too many market restrictions and other barriers to trade and technology adoption. Infrastructure services and investments are deficient and the tax system too concentrated and distorcive. Hence, while these factors persist, it is not likely that the country will grow at sustainable rates comparable to those experienced two decades ago. However, privatization of infrastructure sectors may spur a temporary boom as investment increases to satisfy repressed demand.