Coulomb integrals and conformal blocks in the AdS3-WZNW model

We study spectral flow preserving four-point correlation functions in the AdS3-WZNW model using the Coulomb gas method on the sphere. We present a multiple integral realization of the conformal blocks and explicitly compute amplitudes involving operators with quantized values of the sum of their spins, i.e., requiring an integer number of screening charges of the first kind. The result is given as a sum over the independent configurations of screening contours yielding a monodromy invariant expansion in powers of the worldsheet moduli. We then examine the factorization limit and show that the leading terms in the sum can be identified, in the semiclassical limit, with products of spectral flow conserving three-point functions. These terms can be rewritten as the m-basis version of the integral expression obtained by J. Teschner from a postulate for the operator product expansion of normalizable states in the H3+-WZNW model. Finally, we determine the equivalence between the factorizations of a particular set of four-point functions into products of two three-point functions either preserving or violating spectral flow number conservation. Based on this analysis we argue that the expression for the amplitude as an integral over the spin of the intermediate operators holds beyond the semiclassical regime, thus corroborating that spectral flow conserving correlators in the AdS3-WZNW model are related by analytic continuation to correlation functions in the H3+-WZNW model.Comment: 28 pages; references modified, published versio

Coulomb integrals for the SL(2,R) WZNW model

We review the Coulomb gas computation of three-point functions in the SL(2,R) WZNW model and obtain explicit expressions for generic states. These amplitudes have been computed in the past by this and other methods but the analytic continuation in the number of screening charges required by the Coulomb gas formalism had only been performed in particular cases. After showing that ghost contributions to the correlators can be generally expressed in terms of Schur polynomials we solve Aomoto integrals in the complex plane, a new set of multiple integrals of Dotsenko-Fateev type. We then make use of monodromy invariance to analytically continue the number of screening operators and prove that this procedure gives results in complete agreement with the amplitudes obtained from the bootstrap approach. We also compute a four-point function involving a spectral flow operator and we verify that it leads to the one unit spectral flow three-point function according to a prescription previously proposed in the literature. In addition, we present an alternative method to obtain spectral flow non-conserving n-point functions through well defined operators and we prove that it reproduces the exact correlators for n=3. Independence of the result on the insertion points of these operators suggests that it is possible to violate winding number conservation modifying the background charge.Comment: Improved presentation. New section on spectral flow violating correlators and computation of a four-point functio

Estudio de tres técnicas de concentración de proteína para la determinación del perfil proteico en Condensado de Aire Exhalado

Comunicaciones a congreso

El desarrollo de la profesionalidad docente mediante redes

Desde 2001, un grupo de profesores representantes de distintos centros de educación secundaria del área de Barcelona, se han articulado en red coordinados por el Grupo Observatori d'Oportunitats Educatives de la Universidad Autònoma de Barcelona. El eje del trabajo en red en este período se centró en el análisis de la intervención educativa que reciben los alumnos con dificultades académicas y sociales. El propósito central de esta comunicación es presentar una validación del trabajo realizado durante este período de tiempo, a partir de las consideraciones de los profesores participantes en dicha red. En este sentido, la referencia de la reflexión al contexto social, administrativo y político de la Educción en Catalunya es un factor esencial para comprender aquella validación en todo su sentido

Fusion rules and four-point functions in the AdS3 WZNW model

We study the operator product expansion in the AdS$_3$ WZNW model. The OPE of primary fields and their spectral flow images is computed from the analytic continuation of the expressions in the H$_3^+$ WZNW model, adding spectral flow. We argue that the symmetries of the affine algebra require a truncation which establishes the closure of the fusion rules on the Hilbert space of the theory. Although the physical mechanism determining the decoupling is not completely understood, we present several consistency checks on the results. A preliminary analysis of factorization allows to obtain some properties of four-point functions involving fields in generic sectors of the theory, to verify that they agree with the spectral flow selection rules and to show that the truncation must be realized in physical amplitudes for consistency.Comment: 37 pages, 5 figures, version to appear in Physical Review

Closed string radiation from moving D-branes

We compute the amplitude for the radiation of massless NS-NS closed string states from the interaction of two moving D-branes. We consider particle-like D-branes with reference to 4-dimensional spacetime, in toroidal and orbifold compactifications, and we work out the relevant world sheet propagators within the moving boundary state formalism. We find no on-shell axion emission. For large inter-brane separation, we compute the spacetime graviton emission amplitude and estimate the average energy radiated, whereas the spacetime dilaton amplitude is found to vanish in this limit. The possibility of emission of other massless states depends on the nature of the branes and of the compactification scheme.Comment: 41 pages, LaTe

Interaction of moving D-branes on orbifolds

We use the boundary state formalism to study the interaction of two moving identical D-branes in the Type II superstring theory compactified on orbifolds. By computing the velocity dependence of the amplitude in the limit of large separation we can identify the nature of the different forces between the branes. In particular, in the Z_3 orbifold case we find a boundary state which is coupled only to the N=2 graviton multiplet containing just a graviton and a vector like in the extremal Reissner-Nordstr\"{o}m configuration. We also discuss other cases including $T_4/Z_2$.Comment: 15 pages, Revtex, no figure

Superficial sedimentary stocks and sources of carbon and nitrogen in coastal vegetated assemblages along a flow gradient

Coastal vegetated ecosystems are major organic carbon (OC) and total nitrogen (TN) sinks, but the mechanisms that regulate their spatial variability need to be better understood. Here we assessed how superficial sedimentary OC and TN within intertidal vegetated assemblages (saltmarsh and seagrass) vary along a flow gradient, which is a major driver of sediment grain size, and thus of organic matter (OM) content. A significant relationship between flow current velocity and OC and TN stocks in the seagrass was found, but not in the saltmarsh. OC and TN stocks of the saltmarsh were larger than the seagrass, even though that habitat experiences shorter hydroperiods. Mixing models revealed that OM sources also varied along the flow gradient within the seagrass, but not in the saltmarsh, showing increasing contributions of microphytobenthos (17-32%) and decreasing contributions of POM (45-35%). As well, OM sources varied vertically as microphytobenthos contribution was highest at the higher intertidal saltmarsh (48%), but not POM (39%). Macroalgae, seagrass and saltmarsh showed low contributions. Local trade-offs between flow current velocities, hydroperiod and structural complexity of vegetation must be considered, at both horizontal and vertical (elevation) spatial dimensions, for better estimates of blue carbon and nitrogen in coastal ecosystems.Foundation of Science and Technology of Portugal (FCT) PTDC/MAR-EST/3223/2014 UID/Multi/04326/2013 FCT UID/MAR/00350/2018 SFRH/BPD/119344/2016info:eu-repo/semantics/publishedVersio

El desarrollo de la profesionalidad docente mediante redes

Desde 2001, un grupo de profesores representantes de distintos centros de educación secundaria del área de Barcelona, se han articulado en red coordinados por el Grupo Observatori d'Oportunitats Educatives de la Universidad Autònoma de Barcelona. El eje del trabajo en red en este período se centró en el análisis de la intervención educativa que reciben los alumnos con dificultades académicas y sociales. El propósito central de esta comunicación es presentar una validación del trabajo realizado durante este período de tiempo, a partir de las consideraciones de los profesores participantes en dicha red. En este sentido, la referencia de la reflexión al contexto social, administrativo y político de la Educción en Catalunya es un factor esencial para comprender aquella validación en todo su sentido

Effects of classical PKC activation on hippocampal neurogenesis and cognitive performance: mechanism of action

Hippocampal neurogenesis has widely been linked to memory and learning performance. New neurons generated from neural stem cells (NSC) within the dentate gyrus of the hippocampus (DG) integrate in hippocampal circuitry participating in memory tasks. Several neurological and neuropsychiatric disorders show cognitive impairment together with a reduction in DG neurogenesis. Growth factors secreted within the DG promote neurogenesis. Protein kinases of the protein kinase C (PKC) family facilitate the release of several of these growth factors, highlighting the role of PKC isozymes as key target molecules for the development of drugs that induce hippocampal neurogenesis. PKC activating diterpenes have been shown to facilitate NSC proliferation in neurogenic niches when injected intracerebroventricularly. We show in here that long-term administration of diterpene ER272 promotes neurogenesis in the subventricular zone and in the DG of mice, affecting neuroblasts differentiation and neuronal maturation. A concomitant improvement in learning and spatial memory tasks performance can be observed. Insights into the mechanism of action reveal that this compound facilitates classical PKCα activation and promotes transforming growth factor alpha (TGFα) and, to a lesser extent, neuregulin release. Our results highlight the role of this molecule in the development of pharmacological drugs to treat neurological and neuropsychiatric disorders associated with memory loss and a deficient neurogenesis.Ministerio de Ciencia, Innovación y Universidades de España (MICINN) RTI-2018-099908-B-C21 y RTI-2018-099908-B-C22Ministerio de Ciencia, Innovación y Universidades de España y Fondos FEDER de la Unión Europea (MICINN/FEDER) BFU2016-75038RConsejería de Economía, Conocimiento, Empresas y Universidades de la Junta de Andalucía y Fondos FEDER. FEDER-UCA18-10664