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

Hartree approximation in curved spacetimes revisited II: The semiclassical Einstein equations and de Sitter self-consistent solutions

We consider the semiclassical Einstein equations (SEE) in the presence of a quantum scalar field with self-interaction $\lambda\phi^4$. Working in the Hartree truncation of the two-particle irreducible (2PI) effective action, we compute the vacuum expectation value of the energy-momentum tensor of the scalar field, which act as a source of the SEE. We obtain the renormalized SEE by implementing a consistent renormalization procedure. We apply our results to find self-consistent de Sitter solutions to the SEE in situations with or without spontaneous breaking of the $Z_2$-symmetry.Comment: 32 pages, 4 figure

Characterization of TrxC, an Atypical Thioredoxin Exclusively Present in Cyanobacteria

Cyanobacteria form a diverse group of oxygenic photosynthetic prokaryotes considered to be the antecessor of plant chloroplast. They contain four different thioredoxins isoforms, three of them corresponding to m, x and y type present in plant chloroplast, while the fourth one (named TrxC) is exclusively found in cyanobacteria. TrxC has a modified active site (WCGLC) instead of the canonical (WCGPC) present in most thioredoxins. We have purified it and assayed its activity but surprisingly TrxC lacked all the classical activities, such as insulin precipitation or activation of the fructose-1,6-bisphosphatase. Mutants lacking trxC or over-expressing it were generated in the model cyanobacterium Synechocystis sp. PCC 6803 and their phenotypes have been analyzed. The ΔtrxC mutant grew at similar rates to WT in all conditions tested although it showed an increased carotenoid content especially under low carbon conditions. Overexpression strains showed reduced growth under the same conditions and accumulated lower amounts of carotenoids. They also showed lower oxygen evolution rates at high light but higher Fv’/Fm’ and Non-photochemical-quenching (NPQ) in dark adapted cells, suggesting a more oxidized plastoquinone pool. All these data suggest that TrxC might have a role in regulating photosynthetic adaptation to low carbon and/or high light conditions.España, MINECO BIO2016-75634-PJunta de Andalucía P12-BIO-1119 , BIO-28

Diseño de un sistema de disipación de energía para un edifico en altura

Se considera en este trabajo un edificio sismorresistente aporticado de hormigón armado, de 21 niveles, diseñado para Guayaquil, Ecuador. El objetivo del estudio es desarrollar un procedimiento de diseño de un sistema de disipación pasiva de energía (barras de pandeo restringido) para mejorar los parámetros de respuesta de la estructura original. Se diseñan los disipadores según el procedimiento que se explicita, y luego se realiza un análisis dinámico de historia en el tiempo para la estructura con / sin disipadores, bajo la excitación de 5 acelerogramas. Los resultados del modelo numérico muestran la eficiencia del sistema de disipación propuesto.Postprint (published version

Characterization of photodectors using a monochromator and a broadband light source in the xyz color space

ABSTRACT: Abstract- Photodetectors are sensors, which respond to the electromagnetic radiation of the spectrum. Their spectral response depends on many factors of the manufacturing process, e.g. the type of diode that is used or, in some cases, the optical elements that are added to limit the response band. In this paper, we propose an experimental methodology to obtain the spectral response of a photodetector by constructing the characteristic curve using the monochromatic response. For this purpose, we use a broadband source as input of the monochromator to vary the wavelength each five nm. The characteristic curves of one commercial color sensor were obtained (including the loss) using the output ratio of the monochromator. Via the numerical expression of the response curve, it is possible to model the actual response of the photodetectors to known or simulated spectra of electromagnetic radiation, and thus to generalize photometric measurements. Previously we have demonstrated the importance of obtaining such measurements to study light sources. Finally, this newly developed method helps studying the behavior of a photodetector in detail; hence, it enables the derivation of photometric measurements from known data or simulations

Composición y Método Cinético de Medición de la Actividad Lipasa

Número de publicación: ES2358029 A1 (05.05.2011) También publicado como: ES2358029 B2 (23.03.2012 Número de Solicitud: Consulta de Expedientes OEPM (C.E.O.) P200902117(20.10.2009)La presente invención pertenece al campo de las composiciones químicas utilizadas en métodos de determinación de actividad enzimática. En particular, la presente invención se encuadra en los métodos cinéticos de determinación de la actividad lipasa que utilizan sustratos sintéticos.Universidad de Almerí

Celdilla de digestión-Lixiviación con membrana semipermeable, sistema de cerrado hermético y de control de temperatura

Número de publicación: ES2524521 A1 (09.12.2014) También publicado como: ES2524521 B1 (13.10.2015)ES2524521 B8 (13.05.2016) Número de Solicitud: Consulta de Expedientes OEPM (C.E.O.) P201201027 (08.10.2012)La invención es una celdilla de digestión-lixiviación con membrana semipermeable, sistema de cerrado hermético y de control de temperatura que es un dispositivo para pruebas de digestibilidad y lixiviación de moléculas o iones a nivel laboratorio. La invención es un diseño novedoso que permite mantener aislada la cámara interna (donde se realiza la digestión-lixiviación de materiales) de la cámara externa (donde se reciben los productos de la digestión-lixiviación) conectadas exclusivamente a través de la membrana semipermeable, de tamaño de poro intercambiable, para el paso de las moléculas o iones de tamaño deseado. La celdilla contiene un dispositivo que permite mantener un control de la temperatura en el interior de la cámara interna. Las aplicaciones de la celdilla están en laboratorios académicos o de investigación (empresas, centros de investigación, institutos, Universidades) para la realización de pruebas de digestibilidad in vitro de macromoléculas o de lixiviación de moléculas o iones.Universidad de Almerí