Axial-vector mesons from τ→APντ\tau\to AP\nu_\tau decays

Axial-vector mesons $a_1(1260)$, $f_1(1285)$, $h_1(1170)$, $K_1(1270)$, and $K_1(1400)$ can be produced in semileptonic $\tau\to A P \nu_{\tau}$ decays, where $P$ stands for the pseudoscalar mesons $\pi$ or $K$. We calculate the branching ratios based in a meson dominance model. The exclusive channels $\tau^-\to a_1(1260)^-\pi^0\nu$, $\tau^-\to a_1(1260)^0\pi^-\nu$, and $\tau^-\to h_1(1170)\pi^-\nu$ turn out to be of order ${\cal O}(10^{-3})$, the channel $\tau^-\to f_1(1285)\pi^-\nu$ of order ${\cal O}(10^{-4})$, and channels $\tau^-\to K_1(1270)^-\pi^0\nu$, $\tau^-\to K_1(1270)^0\pi^-\nu$, $\tau^-\to K_1(1400)^-\pi^0\nu$, and $\tau^-\to K_1(1400)^0\pi^-\nu$ of order ${\cal O}(10^{-6})$. These results indicate that the branching ratios could be measured in experiments.Comment: 7 pages, 1 table, 1 figure, version published in PR

Exponential Mixing for a Stochastic PDE Driven by Degenerate Noise

We study stochastic partial differential equations of the reaction-diffusion type. We show that, even if the forcing is very degenerate (i.e. has not full rank), one has exponential convergence towards the invariant measure. The convergence takes place in the topology induced by a weighted variation norm and uses a kind of (uniform) Doeblin condition.Comment: 10 pages, 1 figur

Searching for star-forming dwarf galaxies in the Antlia cluster

The formation and evolution of dwarf galaxies in clusters need to be understood, and this requires large aperture telescopes. In this sense, we selected the Antlia cluster to continue our previous work in the Virgo, Fornax, and Hydra clusters and in the Local Volume (LV). Because of the scarce available literature data, we selected a small sample of five blue compact dwarf (BCD) candidates in Antlia for observation. Using the Gemini South and GMOS camera, we acquired the Halpha imaging needed to detect star-forming regions in this sample. With the long-slit spectroscopic data of the brightest seven knots detected in three BCD candidates, we derived their basic chemical properties. Using archival VISTA VHS survey images, we derived K_S magnitudes and surface brightness profile fits for the whole sample to assess basic physical properties. FS90-98, FS90-106, and FS90-147 are confirmed as BCDs and cluster members, based on their morphology, K_S surface photometry, oxygen abundance, and velocity redshift. FS90-155 and FS90-319 did not show any H{\alpha} emission, and they could not be confirmed as dwarf cluster star-forming galaxies. Based on our data, we studied some fundamental relations to compare star forming dwarfs (BCDs and dIs) in the LV and in the Virgo, Fornax, Hydra, and Antlia clusters. Star-forming dwarfs in nearby clusters appear to follow same fundamental relations in the near infrared with similar objects in the LV, specifically the size-luminosity and the metallicity-luminosity, while other more fundamental relations could not be checked in Antlia due to lack of data.Comment: Accepted for publication in A&A (early 2014

Detrital zircon SHRIMP U-Pb age study of the Cordillera Darwin Metamorphic Complex of Tierra del Fuego : sedimentary sources and implications for the evolution of the Pacific margin of Gondwana

The Cordillera Darwin Metamorphic Complex in the southernmost Andes includes a basement of probable Palaeozoic age, a mid-Jurassic and younger volcano-sedimentary cover, and a suite of Jurassic granites, all of which were jointly metamorphosed during the Cretaceous. Detrital zircon ages presented here show that some of the amphibolite-facies metamorphic rocks previously mapped as basement have a Jurassic protolith. Overall the detrital zircon age patterns for samples of the Cordillera Darwin basement differ from those of the Madre de Dios Terrane of the western Patagonian Andes with which they had been correlated; instead, they are more comparable with those from the Eastern Andes Metamorphic Complex, which apparently developed in a passive margin setting. The paucity of Cambrian detrital zircons indicates that the meta-igneous basement of the Magallanes foreland basin of central and northern Tierra del Fuego was not the main source of detritus for the protolith of the Cordillera Darwin Metamorphic Complex. The possibility is envisaged that the Magallanes Fagnano transform fault boundary between the Scotia and South America plates resulted from reactivation of an older, pre-Jurassic suture zone between the basement terranes of north–central Tierra del Fuego and Cordillera Darwin

Simplified Metrics Calculation for Soft Bit Detection in DVB-T2

The constellation rotation and cyclic quadrature component delay (RQD) technique has been adopted in the second generation terrestrial digital video broadcasting (DVB-T2) standard. It improves the system performance under severe propagation conditions, but introduces serious complexity problems in the hardware implementation of the detection process. In this paper, we present a simplified scheme that greatly reduces the complexity of the demapper by simplifying the soft bit metrics computation having a negligible overall system performance loss

A submillimeter search for pre- and proto-brown dwarfs in Chamaeleon II

Context. Chamaeleon II molecular cloud is an active star forming region that offers an excellent opportunity for studying the formation of brown dwarfs in the southern hemisphere. Aims. Our aims are to identify a population of pre- and proto- brown dwarfs (5 sigma mass limit threshold of ~0.015 Msun) and provide information on the formation mechanisms of substellar objects. Methods. We performed high sensitivity observations at 870 microns using the LABOCA bolometer at the APEX telescope towards an active star forming region in Chamaeleon II. The data are complemented with an extensive multiwavelength catalogue of sources from the optical to the far-infrared to study the nature of the LABOCA detections. Results. We detect fifteen cores at 870 microns, and eleven of them show masses in the substellar regime. The most intense objects in the surveyed field correspond to the submillimeter counterparts of the well known young stellar objects DK Cha and IRAS 12500-7658. We identify a possible proto-brown dwarf candidate (ChaII-APEX-L) with IRAC emission at 3.6 and 4.5 microns. Conclusions. Our analysis indicates that most of the spatially resolved cores are transient, and that the point-like starless cores in the sub-stellar regime (with masses between 0.016 Msun and 0.066 Msun) could be pre-brown dwarfs cores gravitationally unstable if they have radii smaller than 220 AU to 907 AU (1.2" to 5" at 178 pc) respectively for different masses. ALMA observations will be the key to reveal the energetic state of these pre-brown dwarfs candidates.Comment: 11 pages, 6 figure

Influencia del tiempo de gelificación sobre las propiedades estructurales, vibracionales y eléctricas del compósito PEG0.2/V2O5

Se estudiaron las propiedades estructurales, vibracionales y eléctricas de películas V2O5·nH2O y PEG0.2/V2O5 en función del tiempo de gelificación. Las películas fueron sinterizadas por sol-gel mediante la ruta del pentóxido de vanadio sobre sustratos de vidrio previamente tratados. La caracterización se llevo a cabo mediante Difracción de Rayos-X, Espectroscopía Raman y el método de las cuatro puntas convencional de van der Pauw. Los resultados indican que el aumento en el tiempo de gelificación del sol precursor (V2O5.nH2O) incrementa la calidad cristalina, el grado de hidratación, y la concentración de iones V5+ en las películas. En el compósito híbrido (PEG0.2/V2O5) los iones VO2+ actúan como enlazantes entre las cadenas poliméricas haciéndolas más compactas, lo cual facilita la movilidad de los portadores de carga eléctrica entre los iones vanadios. Los resultados mostraron una transición de fase semiconductormetal alrededor de 34°C, una transición óptica del tipo indirecta (para V2O5·nH2O) y una transición vítrea alrededor de Tg=-69°C.Structural, vibrational and electrical properties of V2O5·nH2O and PEG0.2/V2O5 films as a function of gelation time were studied. The films were sintered by sol-gel using vanadium pentoxide route on glass substrates previously treated. Films were characterized by X-Ray Diffraction, Raman Spectroscopy and the four-point van der Pauw conventional method. The results indicated that when the gelation time of the precursor (V2O5·nH2O) is increased, the crystalline quality, the degree of hydration, and V5+ ion concentration are increased. In the hybrid composite (PEG0.2/V2O5), VO2+ ions act as bonding between the polymer chains, making them more compact to facilitate the mobility of electric charge carriers between vanadium ions. The results showed a semiconductor-metal transition about 34°C, an indirect optical transition (V2O5·nH2O) and a vitreous transition around Tg=-69°C.Fil: Londoño Calderon, Cesar Leandro. Universidad Nacional de Colombia; Colombia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jurado, J. F.. Universidad Nacional de Colombia; ColombiaFil: Vargas Hernández, C.. Universidad Nacional de Colombia; Colombi