Heavy Meson Masses in the \epsilon-Regime of HM\chi PT

The pseudoscalar and vector heavy meson masses are calculated in the \epsilon-regime of Heavy Meson Chiral Perturbation Theory to order \epsilon^4. The results of this calculation will allow the determination of low-energy coefficients (LECs) directly from Lattice QCD calculations of the heavy mesons masses for lattices that satisfy the \epsilon-regime criteria. In particular, the LECs that parametrize the NLO volume dependance of the heavy meson masses are necessary for evaluating the light pseudoscalar meson (\pi, K, \eta) and heavy meson ({D^0, D^+, D^+_s}, {B^-,\bar{B}^0,\bar{B}^0_s}) scattering phase shifts.Comment: 16 pages, 6 figure

Nuclear Reactions from Lattice QCD

One of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low- energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.Comment: 35 pages, 13 figures, 1 table, review article for the "Nuclear Reactions from Lattice QCD" workshop hosted by the Institute for Nuclear Theory on March 2013; version 2 includes updated references and extended discussion of previous wor

Moving Multi-Channel Systems in a Finite Volume with Application to Proton-Proton Fusion

The spectrum of a system with multiple channels composed of two hadrons with nonzero total momentum is determined in a finite cubic volume with periodic boundary conditions using effective field theory methods. The results presented are accurate up to exponentially suppressed corrections in the volume due to the finite range of hadronic interactions. The formalism allows one to determine the phase shifts and mixing parameters of pipi-KK isosinglet coupled channels directly from Lattice Quantum Chromodynamics. We show that the extension to more than two channels is straightforward and present the result for three channels. From the energy quantization condition, the volume dependence of electroweak matrix elements of two-hadron processes is extracted. In the non-relativistic case, we pay close attention to processes that mix the 1S0-3S1 two-nucleon states, e.g. proton-proton fusion (pp -> d+ e^+ + nu_e), and show how to determine the transition amplitude of such processes directly from lattice QCD.Comment: 20 pages, 3 figure

First Large-scale Herbig–Haro Jet Driven by a Proto-brown Dwarf

We report the discovery of a new Herbig–Haro jet, HH 1165, in SOAR narrow-band imaging of the vicinity of the σ Orionis cluster. HH 1165 shows a spectacular extended and collimated spatial structure, with a projected length of 0.26 pc, a bent C-shaped morphology, multiple knots, and fragmented bow shocks at the apparent ends of the flow. The Hα image shows a bright halo with a clumpy distribution of material seen around the driving source, and curved reflection nebulosity tracing the outflow cavities. The driving source of HH 1165 is a Class I proto-brown dwarf, Mayrit 1701117 (M1701117), with a total (dust+gas) mass of ~36 M Jup and a bolometric luminosity of ~0.1 L ⊙. High-resolution VLT/UVES spectra of M1701117 show a wealth of emission lines indicative of strong outflow and accretion activity. SOAR/Goodman low-resolution spectra along the jet axis show an asymmetrical morphology for HH 1165. We find a puzzling picture wherein the northwest part exhibits a classical HH jet running into a pre-dominantly neutral medium, while the southern part resembles an externally irradiated jet. The C-shaped bending in HH 1165 may be produced by the combined effects from the massive stars in the ionization front to the east, the σ Orionis core to the west, and the close proximity to the B2-type star HR 1950. HH 1165 shows all of the signatures to be considered as a scaled-down version of parsec-length HH jets, and can be termed as the first sub-stellar analog of a protostellar HH jet system

Decentralizing UNIX abstractions in the exokernel architecture

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 49-51).by Héctor Manuel Briceño Pulido.M.Eng

Elemental abundances of low-mass stars in the young clusters 25 Ori and lambda Ori

Aims. We aim to derive the chemical pattern of the young clusters 25 Orionis and lambda Orionis through homogeneous and accurate measurements of elemental abundances. Methods. We present FLAMES/UVES observations of a sample of 14 K-type targets in the 25 Ori and lambda Ori clusters; we measure their radial velocities, in order to confirm cluster membership. We derive stellar parameters and abundances of Fe, Na, Al, Si, Ca, Ti, and Ni using the code MOOG. Results. All the 25 Ori stars are confirmed cluster members without evidence of binarity; in lambda Ori we identify one non-member and one candidate single-lined binary star. We find an average metallicity [Fe/H]=-0.05+/-0.05 for 25 Ori, where the error is the 1sigma standard deviation from the average. lambda Ori members have a mean iron abundance value of 0.01+/-0.01. The other elements show close-to-solar ratios and no star-to-star dispersion. Conclusions. Our results, along with previous metallicity determinations in the Orion complex, evidence a small but detectable dispersion in the [Fe/H] distribution of the complex. This appears to be compatible with large-scale star formation episodes and initial non-uniformity in the pre-cloud medium. We show that, as expected, the abundance distribution of star forming regions is consistent with the chemical pattern of the Galactic thin disk.Comment: Accepted by Astronomy and Astrophysics. 14 pages, 10 figures, 7 table

17 new very low-mass members in Taurus. The brown dwarf deficit revisited

Recent studies of the substellar population in the Taurus cloud have revealed a deficit of brown dwarfs (BD) compared to the Trapezium cluster population (Briceno et al 1998; Luhman 2000; Luhman et al 2003a; Luhman 2004). However, these works have concentrated on the highest stellar density regions of the Taurus cloud. We have performed a large scale optical survey of this region, covering a total area of 30 deg^2, and encompassing the densest part of the cloud as well as their surroundings, down to a mass detection limits of 15 Jupiter Masses (MJ). In this paper, we present the optical spectroscopic follow-up observations of 97 photometrically selected potential new low-mass Taurus members, of which 27 are strong late-M (SpT < M4V) candidates. These observations reveal 5 new very low mass (VLM) Taurus members and 12 new BDs. Combining our observations with previously published results, we derive an updated substellar to stellar ratio in Taurus of Rss =0.23 +/- 0.05. This ratio now appears consistent with the value previously derived in the Trapezium cluster under similar assumptions of 0.26 +/- 0.04. We find strong indication that the relative numbers of BDs with respect to stars is decreased by a factor 2 in the central regions of the aggregates with respect to the more distributed population. Our findings are best explained in the context of the embryo-ejection model where brown dwarfs originate from dynamical interactions in small N unstable multiple systems.Comment: 20 pages, 15 figure

Conocimiento didáctico de los profesores de tecnología antecedentes de la investigación

This article is part of the doctoral thesis “Didactic Knowledge of the content of technology teachers involved in the learning network REDOTIC”, teaching based on knowledge of content, virtual networks for teaching and learning and technological knowledge. The text socializes the academic background of the research conducted in the field of teaching the content knowledge, understanding it as an organizing construct of a cognitive system of knowledge, beliefs, skills, abilities and capabilities. The research aims to characterize the teaching of content knowledge of technology teachers that are part of REDOTIC, from three categories, which are considered as structural: The knowledge of the contents of the object or fieldof education, it means the disciplinary content knowledge, students ideas and the teaching strategies applied through virtual learning network.El presente artículo se enmarca en la tesis doctoral “Conocimiento didáctico del contenido de los profesores de tecnología que participan en la red de aprendizaje REDOTIC”, fundamentada en el conocimiento didáctico del contenido, las redes virtuales de enseñanza y aprendizaje y el conocimiento tecnológico. En el texto se socializan los antecedentes en relación con las investigaciones realizadas en el campo del conocimiento didáctico del contenido, entendiéndolo como un constructo organizador de un sistema cognitivo de saberes, creencias, destrezas, habilidades y capacidades. La investigación pretende caracterizar el conocimiento didáctico del contenido de los profesores de tecnología que hacen parte de REDOTIC, a partir de tres de las categorías que se consideran estructurales y son: el conocimiento de los contenidos del objeto o materia de enseñanza, es decir, el conocimiento del contenido disciplinar; las ideas de los estudiantes y las estrategias metodológicas para enseñar a través de la red virtual de aprendizaje

Optical spectra of selected Chamaeleon I young stellar objects

We present optical spectra of eight candidate brown dwarfs and a previously known T Tauri star (Sz 33) of the Chamaeleon I dark cloud. We derived spectral types based on the strength of the TiO or VO absorption bands present in the spectra of these objects as well as on the PC3 index of Martin et al. (1999). Photometric data from the literature are used to estimate the bolometric luminosities for these sources. We apply D'Antona & Mazzitelli (1997) pre-main sequence evolutionary tracks and isochrones to derive masses and ages. Based on the presence of Halpha in emission, we confirm that most of the candidates are young objects. Our sample however includes two sources for which we can only provide upper limits for the emission in Halpha; whereas these two objects are most likely foreground/background stars, higher resolution spectra are required to confirm their true nature. Among the likely cloud members, we detect one new sub-stellar object and three transition stellar/sub-stellar sources.Comment: 22 pages - manuscript forma