Nestings of rational homogeneous varieties

In this paper we study the existence of sections of universal bundles on rational homogeneous varieties -- called nestings -- classifying them completely in the case in which the Lie algebra of the automorphism group of the variety is simple of classical type. In particular we show that, under this hypothesis, nestings do not exist unless there exists a proper algebraic subgroup of the automorphism group acting transitively on the base variety.Comment: Major revision of the exposition. To appear in Tranformation Group

Rank two Fano bundles on G(1,4)

We classify rank two Fano bundles over the Grassmannian of lines \G(1,4). In particular we show that the only non-split rank two Fano bundle over \G(1,4) is, up to a twist, the universal quotient bundle \cQ. This completes the classification of rank two Fano bundles over Grassmannians of lines

Impact of Higgs physics on the parameter space of the μνSSM

Given the increasing number of experimental data, together with the precise measurement of the properties of the Higgs boson at the LHC, the parameter space of supersymmetric models starts to be constrained. We carry out a detailed analysis of this issue in the framework of the μνSSM. In this model, three families of right-handed neutrino superfields are present in order to solve the μ problem and simultaneously reproduce neutrino physics. The new couplings and sneutrino vacuum expectation values in the μνSSM induce new mixing of states, and, in particular, the three right sneutrinos can be substantially mixed with the neutral Higgses. After diagonalization, the masses of the corresponding three singlet-like eigenstates can be smaller or larger than the mass of the Higgs, or even degenerated with it. We analyze whether these situations are still compatible with the experimental results. To address it we scan the parameter space of the Higgs sector of the model. In particular, we sample the μνSSM using a powerful likelihood data-driven method, paying special attention to satisfy the constraints coming from Higgs sector measurements/limits (using HiggsBounds and HiggsSignals), as well as a class of flavor observables such as B and μ decays, while muon g- 2 is briefly discussed. We find that large regions of the parameter space of the μνSSM are viable, containing an interesting phenomenology that could be probed at the LHCThe work of EK and CM was supported in part by the Spanish Agencia Estatal de Investigación through the grants FPA2015-65929-P (MINECO/FEDER, UE), PGC2018-095161-B-I00 and IFT Centro de Excelencia Severo Ochoa SEV-2016-0597. The work of EK was funded by Fundación La Caixa under ‘La Caixa-Severo Ochoa’ international predoctoral grant. The work of DL was supported by the Argentinian CONICET, and also acknowledges the support of the Spanish grant FPA2015-65929-P (MINECO/FEDER, UE). RR acknowledges partial funding/support from the Elusives ITN (Marie Sklodowska-Curie grant agreement No 674896), the “SOM Sabor y origen de la Materia” (FPA 2017-85985-P) and the Spanish MINECO Centro de Excelencia Severo Ochoa del IFIC program under grant SEV-2014-0398. EK, CM, DL and RR also acknowledge the support of the Spanish Red Consolider MultiDark FPA2017-90566-RED

Do broadband and Information and Communication Technologies (ICTS) have a positive impact on school performance? : evidence for CHILE

Spanish version available in IDRC Digital Library: Tienen la banda ancha y las TIC un impacto positivo en el rendimiento escolar? : evidencia sobre ChileEven though connectivity actually generates a greater degree of efficiency in the teaching-learning process, test results can fall due to the fact that students can be distracted by having internet access. Access to internet at home shows in general a negative impact upon performance, but having a computer available at home has a positive and significant impact. Traditional evaluation techniques for impact evaluation of ICT in the Classroom programs were used, but results do not identify a significant impact of these programs, either separately or jointly

Tienen la banda ancha y las TIC un impacto positivo en el rendimiento escolar? : evidencia sobre Chile

Versión en inglés disponible en la Biblioteca Digital del IDRC: Do broadband and Information and Communication Technologies (ICTS) have a positive impact on school performance? : evidence for CHILEEn este artículo se estudia el impacto de la conectividad a banda ancha y del uso de tecnologías de la información y la comunicación (TIC) con fines pedagógicos en la calidad de la educación de los estudiantes del ciclo básico de establecimientos educacionales subvencionados (EES) de Chile. Para ello, se estima el impacto de dos iniciativas del Ministerio de Educación (MINEDUC), “Fondos para banda ancha” (2006-2010) y “TIC en aula” (2007-2011) sobre el rendimiento de los estudiantes en las pruebas nacionales estandarizadas de Lenguaje y Matemáticas establecidas por el Sistema de Medición de Calidad de la Educación (SIMCE), disponible desde 1998. La unidad de observación es el estudiante y se analiza el efecto individual, conjunto y focalizado de los programas mencionados sobre cohortes que rinden las evaluaciones en dos momentos del tiempo. La muestra de estudio excluyó EES pertenecientes al grupo socioeconómico alto y, en el caso de “TIC en aula”, se trabajó solo con los municipalizados. Los resultados muestran que los programas no tienen efectos significativos en el rendimiento, ni individual ni conjuntamente, pero sí fue posible identificar efectos positivos de “TIC en aula” en grupos específicos en Lenguaje, no así en Matemáticas

Rank two Fano bundles on G(1, 4)

Abstract We classify rank two Fano bundles over the Grassmannian of lines G(1, 4). In particular we show that the only non-split rank two Fano bundle over

An Atlas of the circumnuclear regions of 75 Seyfert galaxies in the near-UV with HST Advanced Camera for Surveys

We present an atlas of the central regions of 75 Seyfert galaxies imaged in the near-UV with the Advanced Camera for Surveys of the Hubble Space Telescope at an average resolution of ~10pc. These data complement archival high resolution data from the Space Telescope at optical and near-IR wavelengths, creating an extremely valuable dataset for astronomers with a broad range of scientific interests. Our goal is to investigate the nature of the near-UV light in these objects, its relation to the circumnuclear starburst phenomenon, and the connection of this to the evolution and growth of the galaxy bulge and central black hole. In this paper, we describe the near-UV morphology of the objects and characterize the near-UV emission. We estimate the size and the luminosity of the emitting regions and extract the luminosity profile. We also determine the presence of unresolved compact nuclei. In addition, the circumnuclear stellar cluster population is identified, and the contribution of the stellar clusters to the total light, at this wavelength, is estimated. The size of the sample allows us to draw robust statistical conclusions. We find that {Seyfert 1} galaxies are completely dominated by its bright and compact nucleus, that remains point-like at this resolution, while we find almost no unresolved nucleus in Seyfert 2. The Seyfert types 1 and 2 are quite segregated in an asymmetry vs compactness plot. Stellar clusters are found somewhat more frequently in Sy2 (in ~70% of the galaxies) than in Sy1 (~57%), and contribute more to the total light in Sy2, but this two differences seem to be mostly due to the large contribution of the compact nucleus in Sy1, as the luminosity distribution of the clusters is similar in both Sy types.Comment: Accepted for publication in AJ, 58 pages, 20 figures. High-resolution figures for all the objects are available at http://www.iaa.es/~manuel/publications/paper01.htm

Gamma-ray detection from gravitino dark matter decay in the μν\mu\nuSSM

The $\mu\nu$SSM provides a solution to the $\mu$-problem of the MSSM and explains the origin of neutrino masses by simply using right-handed neutrino superfields. Given that R-parity is broken in this model, the gravitino is a natural candidate for dark matter since its lifetime becomes much longer than the age of the Universe. We consider the implications of gravitino dark matter in the $\mu\nu$SSM, analyzing in particular the prospects for detecting gamma rays from decaying gravitinos. If the gravitino explains the whole dark matter component, a gravitino mass larger than 20 GeV is disfavored by the isotropic diffuse photon background measurements. On the other hand, a gravitino with a mass range between 0.1-20 GeV gives rise to a signal that might be observed by the FERMI satellite. In this way important regions of the parameter space of the $\mu\nu$SSM can be checked.Comment: Final version to appear in JCAP, 13 pages, 3 figure