Neutrino masses and mixing in A4 models with three Higgs doublets

We study neutrino masses and mixing in the context of flavor models with A4 symmetry, three scalar doublets in the triplet representation, and three lepton families. We show that there is no representation assignment that yields a dimension-five mass operator consistent with experiment. We then consider a type-I seesaw with three heavy right-handed neutrinos, explaining in detail why it fails, and showing with a numerical example that agreement with the present neutrino oscillation data can be recovered with the inclusion of dimension-three heavy neutrino mass terms that break softly the A4 symmetry.Comment: 10 pages, RevTex, 3 figures. v2: much expanded section on softly broken A4; refs adde

Physical constraints on interacting dark energy models

Physical limits on the equation-of-state (EoS) parameter of a dark energy component non-minimally coupled with the dark matter field are examined in light of the second law of thermodynamics and the positiveness of entropy. Such constraints are combined with observational data sets of type Ia supernovae, baryon acoustic oscillations and the angular acoustic scale of the cosmic microwave background to impose restrictions on the behaviour of the dark matter/dark energy interaction. Considering two EoS parameterisations of the type $w = w_0 + w_a\zeta(z)$, we derive a general expression for the evolution of the dark energy density and show that the combination of thermodynamic limits and observational data provide tight bounds on the $w_0 - w_a$ parameter space.Comment: 7 pages, 4 figures. Accepted for publication in European Physical Journal

Parent Stars of Extrasolar Planets. X. Lithium Abundances and vsini Revisited

We determine Li abundances and vsini values from new spectra of 53 stars with Doppler-detected planets not included in our previous papers in this series. We also examine two sets of stars without detected planets, which together serve as our comparison sample. Using the method of comparison of Li abundances and vsini values between two sets of stars we introduced in Gonzalez (2008), we confirm that these two quantities are smaller among stars with planets compared to stars without detected planets near the solar temperature. The transition from low to high Li abundance among SWPs occurs near 5850 K, a revision of about 50 K from our previous determination. The transition from low to high vsini occurs near 6000 K, but this temperature is not as well constrained.Comment: accepted for publication in MNRAS; 14 pages, 13 figures, 3 table

Biopulpaje, el futuro

- González M, J. ; Silva S., R. ; Morales, R. Departamento de Ingeniería de la Madera, Facultad de Ciencias Forestales. Universidad de ChileCon el fin de conocer las bondades y variables respuestas del biopulpaje Kraft, realizado sobre astillas de mezcla industrial de Eucalyptus (80% globulus, 20% nitens), se trató material de dicha mezcla con dos hongos de pudrición blanca ABA y ETA, durante 30 días a 25º C de temperatura y con un porcentaje de 0,3% de inóculo sobre base peso seco de madera. Una tercera muestra sin tratar fue considerada como testigo. Después del tiempo señalado, se sometieron las astillas a pulpaje Kraft, a 16% de alcali activo, 30% de sulfidez, 5/1 de relación licor/madera y 165º C de temperatura de reposo. Los rendimientos de pulpaje, variaron entre 55,8 y un 56,1% y los testigos, 52,8%. Los Kappas fueron de 13,7, 13,5 y 15,0 respectivamente. Estos resultados, para pulpas crudas de fibra corta, que son la segunda etapa del proyecto FONDEF DO2I-1086 sobre biopulpaje de Eucalyptus, presentan una perspectiva más que atractiva, para los resultados que se deberán obtener, para la implementación de biopulpaje aplicado a trozas industriales y procesos de blanqueamiento

Thermodynamics and dark energy

A significant observational effort has been directed to unveil the nature of the so-called dark energy. However, given the large number of theoretical possibilities, it is possible that such a task cannot be performed on the basis only of the observational data. In this article we discuss some thermodynamic properties of this energy component by assuming that its constituents are massless quanta with a general time-dependent equation-of-state parameter $\omega(z)=\omega_0 + \omega_a f(z)$, where $\omega_0$ and $\omega_a$ are constants and $f(z)$ may assume different forms. We show that very restrictive bounds can be placed on the $w_0$ - $w_a$ space when current observational data are combined with the thermodynamic constraints derived.Comment: 5 pages, 3 figures, LaTe

Pressure effect in the X-ray intrinsic position resolution in noble gases and mixtures

A study of the gas pressure effect in the position resolution of an interacting X- or gamma-ray photon in a gas medium is performed. The intrinsic position resolution for pure noble gases (Argon and Xenon) and their mixtures with CO2 and CH4 were calculated for several gas pressures (1-10bar) and for photon energies between 5.4 and 60.0 keV, being possible to establish a linear match between the intrinsic position resolution and the inverse of the gas pressure in that energy range. In order to evaluate the quality of the method here described, a comparison between the available experimental data and the calculated one in this work, is done and discussed. In the majority of the cases, a strong agreement is observed

Evidence for internal field in graphite: A conduction electron spin resonance study

We report conduction electron spin resonance measurements performed on highly oriented pyrolitic graphite samples between 10 K and 300 K using S (f = 4 GHz), X (f = 9.4 GHz), and Q (f = 34.4 GHz) microwave bands for the external dc-magnetic field applied parallel (H || c) and perpendicular (H perp c) to the sample hexagonal c-axis. The results obtained in the H || c geometry are interpreted in terms of the presence of an effective internal ferromagnetic-like field Heff-int(T,H) that increases as the temperature decreases and the applied dc-magnetic field increases. We associate the occurrence of the Heff-int(T,H) with the field-induced metal-insulator transition in graphite and discuss its origin in the light of relevant theoretical models.Comment: 10 pages (tex), 5 figures (ps

The CHilean Automatic Supernova sEarch (CHASE)

The CHASE project started in 2007 with the aim of providing young southern supernovae (SNe) to the Carnegie Supernova Project (CSP) and Millennium Center for Supernova Studies (MCSS) follow-up programs. So far CHASE has discovered 33 SNe with an average of more than 2.5 SNe per month in 2008. In addition to the search we are carrying out a follow-up program targeting bright SNe. Our fully automated data reduction allows us to follow the evolution on the light curve in real time, triggering further observations if something potentially interesting is detectedComment: 4 pages, 2 figures, conference proceedin

Characterization of the HD 17156 planetary system

AIMS : To improve the parameters of the HD 17156 system (peculiar due to the eccentric and long orbital period of its transiting planet) and constrain the presence of stellar companions. METHODS : Photometric data were acquired for 4 transits, and high precision radial velocity measurements were simultaneously acquired with SARG@TNG for one transit. The template spectra of HD 17156 was used to derive effective temperature, gravity, and metallicity. A fit of the photometric and spectroscopic data was performed to measure the stellar and planetary radii, and the spin-orbit alignment. Planet orbital elements and ephemeris were derived from the fit. Near infrared adaptive optic images was acquired with ADOPT@TNG. RESULTS: We have found that the star has a radius of R_S = 1.43+/-0.03 R_sun and the planet R_P =1.02+/-0.08 R_jup. The transit ephemeris is T_c = 2454\756.73134+/-0.00020+N*21.21663+/-0.00045 BJD. The analysis of the Rossiter-Mclaughlin effect shows that the system is spin orbit aligned with an angle lambda = 4.8 +/- 5.3 deg. The analysis of high resolution images has not revealed any stellar companion with projected separation between 150 and 1000 AU from HD 17156.Comment: submitted to A&