On the renormalization procedure for quantum fields with modified dispersion relation in curved spacetimes

We review our recent results on the renormalization procedure for a free quantum scalar field with modified dispersion relations in curved spacetimes. For dispersion relations containing up to $2s$ powers of the spatial momentum, the subtraction necessary to renormalize $$and$$ depends on $s$. We first describe our previous analysis for spatially flat Friedman-Robertson-Walker and Bianchi type I metrics. Then we present a new power counting analysis for general background metrics in the weak field approximation.Comment: Talk given at the 7th Alexander Friedmann International Seminar on Gravitation and Cosmology, Joao Pessoa, Brazil, July 200

Nonlinear effects of dark energy clustering beyond the acoustic scales

We extend the resummation method of Anselmi & Pietroni (2012) to compute the total density power spectrum in models of quintessence characterized by a vanishing speed of sound. For standard $\Lambda$CDM cosmologies, this resummation scheme allows predictions with an accuracy at the few percent level beyond the range of scales where acoustic oscillations are present, therefore comparable to other, common numerical tools. In addition, our theoretical approach indicates an approximate but valuable and simple relation between the power spectra for standard quintessence models and models where scalar field perturbations appear at all scales. This, in turn, provides an educated guess for the prediction of nonlinear growth in models with generic speed of sound, particularly valuable since no numerical results are yet available.Comment: 28 pages, 12 figure

Extreme parameter sensitivity in quasidilaton massive gravity

We reanalyze the behavior of Friedmann-Lema\^itre-Robertson-Walker cosmologies in the recently proposed quasidilaton massive-gravity model, and discover that the background dynamics present hitherto unreported features that require unexpected fine-tuning of the additional fundamental parameters of the theory for an observationally consistent background cosmology. We also identify new allowed regions in the parameters space and exclude some of the previously considered ones. The evolution of the mass of gravitational waves reveals non-trivial behavior, exhibiting a mass squared that may be negative in the past, and that presently, while positive, is larger than the square of the Hubble parameter. These properties of the gravity-wave mass have the potential to lead to observational tests of the theory. While quasidilaton massive gravity is known to have issues with stability at short distances, the current analysis is a first step toward the investigation of the more stable extended quasidilaton massive gravity theory, with some expectation that both the fine-tuning of parameters and the interesting behavior of the gravity-wave mass will persist.Comment: 10 pages, 7 figure

Massless Interacting Scalar Fields in de Sitter space

We present a method to compute the two-point functions for an $O(N)$ scalar field model in de Sitter spacetime, avoiding the well known infrared problems for massless fields. The method is based on an exact treatment of the Euclidean zero modes and a perturbative one of the nonzero modes, and involves a partial resummation of the leading secular terms. This resummation, crucial to obtain a decay of the correlation functions, is implemented along with a double expansion in an effective coupling constant $\sqrt\lambda$ and in $1/N$. The results reduce to those known in the leading infrared approximation and coincide with the ones obtained directly in Lorentzian de Sitter spacetime in the large $N$ limit. The new method allows for a systematic calculation of higher order corrections both in $\sqrt\lambda$ and in $1/N$.Comment: 8 pages. Summarized version of JHEP 09 (2016) 117 [arXiv:1606.03481]. Published in the Proceedings of the 19th International Seminar on High Energy Physics (QUARKS-2016

O(N)O(N) model in Euclidean de Sitter space: beyond the leading infrared approximation

We consider an $O(N)$ scalar field model with quartic interaction in $d$-dimensional Euclidean de Sitter space. In order to avoid the problems of the standard perturbative calculations for light and massless fields, we generalize to the $O(N)$ theory a systematic method introduced previously for a single field, which treats the zero modes exactly and the nonzero modes perturbatively. We compute the two-point functions taking into account not only the leading infrared contribution, coming from the self-interaction of the zero modes, but also corrections due to the interaction of the ultraviolet modes. For the model defined in the corresponding Lorentzian de Sitter spacetime, we obtain the two-point functions by analytical continuation. We point out that a partial resummation of the leading secular terms (which necessarily involves nonzero modes) is required to obtain a decay at large distances for massless fields. We implement this resummation along with a systematic double expansion in an effective coupling constant $\sqrt\lambda$ and in 1/N. We explicitly perform the calculation up to the next-to-next-to-leading order in $\sqrt\lambda$ and up to next-to-leading order in 1/N. The results reduce to those known in the leading infrared approximation. We also show that they coincide with the ones obtained directly in Lorentzian de Sitter spacetime in the large N limit, provided the same renormalization scheme is used.Comment: 31 pages, 5 figures. Minor changes. Published versio

Efecto del vertido directo de las aguas mieles en la calidad físico-química del agua de la Subcuenca del Río Jigüina, Jinotega

Se hizo un estudio sobre el efecto que causa el vertido directo de las aguas procedentes del beneficiado húmedo del café en la calidad fisicoquímica del agua de la Subcuenca del río Jigüina, ubicada principalmente en el municipio de Jinotega, Nicaragua

Education and immigration in Catalonia: A state of the art

Des del començament del segle xxi, Catalunya ha consolidat la seva posició com a centre d’atracció de població estrangera del sud d’Europa. Així, a 1 de gener de 2010 i d’acord amb les dades preliminars del padró continu, la població de nacionalitat estrangera a Catalunya representava un total d’1. 193. 283 persones —un 15,9 per cent de la població total. L’entrada massiva de població estrangera en el territori i el creixent debat respecte a la qualitat de l’educació han centrat el discurs en els mecanismes d’integració i distribució en el sistema escolar dels nens i joves d’origen estranger. L’objectiu del present treball és el de dur a terme una primera aproximació a la literatura sobre educació i immigració a Catalunya, segons tres temes principals de recerca: incorporació en el sistema educatiu i rendiment escolar; segregació escolar, i, finalment, trajectòries educatives i estudis longitudinals.From the beginning of the 21st Century, Catalonia has consolidated its position as an international migration attraction node in southern Europe. As a result, at January 1st, 2010, 15. 9% of the Catalan population (1’193,283 persons) was of foreign origin. The massive foreign population in-flows and the growing debate on the quality of education have led to focus the attention on the mechanisms of integration and distribution of foreign origin students. The paper’s aim is to present a first approach to the scientific literature on education and international migration in Catalonia on three main fields: access to education and academic performance; school segregation; and, finally, academic trajectories and longitudinal studies.Desde el comienzo del siglo xxi, Cataluña ha consolidado su posición como centro de atracción de población extranjera en el sur de Europa. Así, a 1 de enero de 2010 y de acuerdo con los datos preliminares del padrón continuo, la población de nacionalidad extranjera en Cataluña representaba un total de 1. 193. 283 personas —un 15,9 por ciento de la población total. La entrada masiva de población extranjera en el territorio y el creciente debate respecto a la calidad de la educación han centrado el discurso en los mecanismos de integración y distribución en el sistema escolar de los niños y jóvenes de origen extranjero. El objetivo del presente trabajo es el de llevar a cabo una primera aproximación a la literatura sobre educación e inmigración en Cataluña, diferenciándola según tres temas principales: incorporación en el sistema educativo y rendimiento escolar; segregación escolar, y, finalmente, trayectorias educativas y estudios longitudinales

Educación e inmigración en Cataluña : un estado de la cuestión

Desde el comienzo del siglo xxi, Cataluña ha consolidado su posición como centro de atracción de población extranjera en el sur de Europa. Así, a 1 de enero de 2010 y de acuerdo con los datos preliminares del padrón continuo, la población de nacionalidad extranjera en Cataluña representaba un total de 1.193.283 personas -un 15,9 por ciento de la población total. La entrada masiva de población extranjera en el territorio y el creciente debate respecto a la calidad de la educación han centrado el discurso en los mecanismos de integración y distribución en el sistema escolar de los niños y jóvenes de origen extranjero. El objetivo del presente trabajo es el de llevar a cabo una primera aproximación a la literatura sobre educación e inmigración en Cataluña, diferenciándola según tres temas principales: incorporación en el sistema educativo y rendimiento escolar; segregación escolar, y, finalmente, trayectorias educativas y estudios longitudinales.Des del començament del segle xxi, Catalunya ha consolidat la seva posició com a centre d'atracció de població estrangera del sud d'Europa. Així, a 1 de gener de 2010 i d'acord amb les dades preliminars del padró continu, la població de nacionalitat estrangera a Catalunya representava un total d'1.193.283 persones -un 15,9 per cent de la població total. L'entrada massiva de població estrangera en el territori i el creixent debat respecte a la qualitat de l'educació han centrat el discurs en els mecanismes d'integració i distribució en el sistema escolar dels nens i joves d'origen estranger. L'objectiu del present treball és el de dur a terme una primera aproximació a la literatura sobre educació i immigració a Catalunya, segons tres temes principals de recerca: incorporació en el sistema educatiu i rendiment escolar; segregació escolar, i, finalment, trajectòries educatives i estudis longitudinals.Depuis le début du xxi siècle, la Catalogne a renforcé sa position de focus d'attraction des populations étrangères dans le sud de l'Europe. Ainsi, au premier janvier 2010, et selon les données préliminaires du recensement continu (padrón continuo), la population de nationalité étrangère en Catalogne représentait un total de 1.193.283 personnes, soit 15,9% de la population totale. L'entrée massive de population étrangère sur le territoire et le débat croissant sur la qualité de l'éducation ont centré le discours sur les mécanismes d'intégration et de répartition au sein du système scolaire des élèves d'origine étrangère. L'objectif du présent travail consiste à établir une première approche de la littérature traitant de l'éducation et de l'immigration en Catalogne, au tour de trois thèmes principaux: l'incorporation dans le système éducatif et la performance scolaire; la ségrégation scolaire; finalement, les trajectoires éducatives et les études longitudinales.From the beginning of the 21st Century, Catalonia has consolidated its position as an international migration attraction node in southern Europe. As a result, at January 1st, 2010, 15.9% of the Catalan population (1'193,283 persons) was of foreign origin. The massive foreign population in-flows and the growing debate on the quality of education have led to focus the attention on the mechanisms of integration and distribution of foreign origin students. The paper's aim is to present a first approach to the scientific literature on education and international migration in Catalonia on three main fields: access to education and academic performance; school segregation; and, finally, academic trajectories and longitudinal studies