Warm inflation with back - reaction: a stochastic approach

I study a stochastic approach for warm inflation considering back - reaction of the metric with the fluctuations of matter field. This formalism takes into account the local inhomogeneities fo the spacetime in a globally flat Friedmann - Robertson - Walker metric. The stochastic equations for the fluctuations of the matter field and the metric are obtained. Finally, the dynamics for the amplitude of these fluctuations in a power - law expansion for the universe are examined.Comment: minor changes, 6 pages, no figures, accepted for publication in Classical and Quantum Gravit

Two-fluid evolving Lorentzian wormholes

We investigate the evolution of a family of wormholes sustained by two matter components: one with homogeneous and isotropic properties $\rho(t)$ and another inhomogeneous and anisotropic $\rho_{in}(t,r)$. The rate of expansion of these evolving wormholes is only determined by the isotropic and homogeneous matter component $\rho(t)$. Particularly, we consider a family of exact two-fluid evolving wormholes expanding with constant velocity and satisfying the dominant and the strong energy conditions in the whole spacetime. In general, for the case of vanishing isotropic fluid $\rho(t)$ and cosmological constant $\Lambda$ the space expands with constant velocity, and for $\rho(t)=0$ and $\Lambda \neq 0$ the rate of expansion is determined by the cosmological constant. The considered here two-fluid evolving wormholes are a generalization of single fluid models discussed in previous works of the present authors [Phys.\ Rev.\ D {\bf 78}, 104006 (2008); Phys.\ Rev.\ D {\bf 79}, 024005 (2009)].Comment: 8 pages, to be published in Phys. Rev

SUSY Enhancements in (0,4) Deformations of AdS_3/CFT_2

We discuss a marginal deformation of the SL(2,R) x SU(2) x U(1)^4 WZW model, which describes string theory on AdS_3 x S^3 x T^4, that corresponds to warping the S^3 factor. This deformation breaks part of the N=(4,4) supersymmetry of the undeformed dual CFT to N=(0,4) supersymmetry. In the spirit of work by Giveon, Kutasov, and Seiberg, we construct the asymptotic spacetime symmetry algebra from worldsheet operators and find a restoration of (4,4) supersymmetry at discrete values of the deformation parameter. We explain this result from various perspectives: the worldsheet, supergravity, and from the singular D1-D5 CFT. The supergravity analysis includes an asymptotic symmetry computation of the level of the affine SU(2) R-symmetry, which arises purely from B-field contributions.Comment: 16 pages; v2: references adde

AM-OER: An Agile Method for the Development of Open Educational Resources

Open Educational Resources have emerged as important elements of education in the contemporary society, promoting life-long and personalized learning that transcends social, eco- nomic and geographical barriers. To achieve the potential of OERs and bring impact on education, it is necessary to increase their development and supply. However, one of the current challenges is how to produce quality and relevant OERs to be reused and adapted to different contexts and learning situations. In this paper we proposed an agile method for the development of OERs – AM-OER, grounded on agile practices from Software Engineering. Learning Design practices from the OULDI project (UK Open University) are also embedded into the AM-OER aiming at improving quality and facilitating reuse and adaptation of OERs. In order to validate AM-OER, an experiment was conducted by applying it in the development of an OER on software testing. The results showed preliminary evidences on the applicability, effectiveness and ef ciency of the method in the development of OERs

On the accuracy of Latin American trade statistics: A nonparametric test for 1925

This paper proposes a nonparametric test in order to establish the level of accuracy of the foreign trade statistics of 17 Latin American countries when contrasted with the trade statistics of the main partners in 1925. The Wilcoxon Matched-Pairs Ranks test is used to determine whether the differences between the data registered by exporters and importers are meaningful, and if so, whether the differences are systematic in any direction. The paper tests for the reliability of the data registered for two homogeneous products, petroleum and coal, both in volume and value. The conclusion of the several exercises performed is that we cannot accept the existence of statistically significant differences between the data provided by the exporters and the registered by the importing countries in most cases. The qualitative historiography of Latin American describes its foreign trade statistics as mostly unusable. Our quantitative results contest this view.Latin America, statistical accuracy, international trade data, nonparametric methods, petroleum trade, coal trade.

The impact of maternal BMI, gestational weight gain, and breastfeeding on early childhood weight: Analysis of a statewide WIC dataset

Early childhood obesity is a persistent health concern with more frequent and significant impact on low-income families. Maternal weight factors impact offspring weight status, but evidence on whether breastfeeding protects against this impact is mixed. This analysis examined a model to predict early childhood obesity risk, simultaneously accounting for maternal pre-pregnancy body mass index (BMI), gestational weight gain, and breastfeeding. The team analyzed 27,016 unique maternal-child dyadic records collected via the Supplemental Nutrition Program for Wisconsin Women, Infants, and Children (WIC) between 2009 and 2011. Generalized Linear Modeling, specifically logistic regression, was used to predict a child\u27s risk of obesity given the mother\u27s pre-pregnancy BMI, gestational weight gain, and duration of breastfeeding. For each 1 kg/m2 increase in pre-pregnancy BMI, there was a 4.5% increase in risk of obesity compared to children with mothers of normal BMI. Children whose mothers had excessive gestational weight gain were 50% more likely to have obesity compared to those whose mothers had ideal weight gain. For each week of additional breastfeeding, there was a 1.9% increased risk of obesity. The risk models did not differ by race. In this model, accounting for pre-pregnancy weight, gestational weight gain, and breastfeeding among a diverse, low-income sample, women with pre-pregnancy overweight and obesity or who had excessive gestational weight gain had the highest risk of early childhood obesity. While breastfeeding is healthy for many reasons, providers should focus on maternal weight-related behaviors when counseling mothers about how to avoid risk of early childhood obesity

Energy as an indicator of modernisation in Latin America by 1925

In absence of comparable macroeconomic indicators for most of the Latin American economies beyond the 1930s, this paper presents an estimate of the apparent consumption per head of coal and petroleum for 25 countries of Latin American and the Caribbean for the year 1925, doubling the number of countries for which energy consumption estimates were previously available. Energy consumption is then used as an indicator of economic modernisation. As a result, the paper provides the basis for a quantitative comparative analysis of modernisation performance beyond the few countries for which historical national accounts are available in Latin America.Energy consumption, modernisation, Latin America, petroleum, coal