Friedel oscillations in a Luttinger liquid with long-range interactions

We introduce a path-integral approach that allows to compute charge density oscillations in a Luttinger liquid with impurities. We obtain an explicit expression for the envelope of Friedel oscillations in the presence of arbitrary electron-electron potentials. As examples, in order to illustrate the procedure, we show how to use our formula for contact and Coulomb potentials.Comment: 11 pages, no figures, latex. Revised version to appear in PR

Improved harmonic approximation and the 2D Ising model at T≠TcT\neq T_{c} and h≠0h\neq0

We propose a new method to determine the unknown parameter associated to a self-consistent harmonic approximation. We check the validity of our technique in the context of the sine-Gordon model. As a non trivial application we consider the scaling regime of the 2D Ising model away from the critical point and in the presence of a magnetic field $h$. We derive an expression that relates the approximate correlation length $\xi$, $T-T_c$ and $h$.Comment: 11 pages, Latex, 3 figures. Accepted for publication in Journal of Physics

Classical electromagnetic field theory in the presence of magnetic sources

Using two new well defined 4-dimensional potential vectors, we formulate the classical Maxwell's field theory in a form which has manifest Lorentz covariance and SO(2) duality symmetry in the presence of magnetic sources. We set up a consistent Lagrangian for the theory. Then from the action principle we get both Maxwell's equation and the equation of motion of a dyon moving in the electro-magnetic field.Comment: 10 pages, no figure

Massive Schwinger model and its confining aspects on curved space-time

Using a covariant method to regularize the composite operators, we obtain the bosonized action of the massive Schwinger model on a classical curved background. Using the solution of the bosonic effective action, the energy of two static external charges with finite and large distance separation on a static curved space-time is obtained. The confining behavior of this model is also explicitly discussed.Comment: A disscussion about the infrared regularization and also two references are added. Accepted for publication in Phys. Rev. D (2001

Gaussian Effective Potential and the Coleman's normal-ordering Prescription : the Functional Integral Formalism

For a class of system, the potential of whose Bosonic Hamiltonian has a Fourier representation in the sense of tempered distributions, we calculate the Gaussian effective potential within the framework of functional integral formalism. We show that the Coleman's normal-ordering prescription can be formally generalized to the functional integral formalism.Comment: 6 pages, revtex; With derivation details and an example added. To appear in J. Phys.

Geología del Subsuelo en el Predio del Instituto Nacional de Tecnología Industrial (INTI)

Fil: Boujon, Pamela. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Conde Serra, Alejandro. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Naón, Virginia. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Álvarez, Dolores. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.Fil: Peroni, Javier. Servicio Geológico Minero Argentino. Instituto de Geología y Recursos Minerales; Argentina.A partir del convenio de cooperación e intercambio científico entre el Instituto Nacional de Tecnología Industrial (INTI), el Servicio Geológico Minero Argentino (SEGEMAR) y las Universidades de Urbino, Ferrara y Camerino de Italia se elaboró este primer estudio con el objetivo de conocer las características geológicas e hidrogeológicas del subsuelo del predio del INTI para evaluar la instalación de bombas de calor (geotermia somera). Para ello, se realizó una búsqueda de perforaciones referentes y aledañas, así mismo se ejecutaron Sondeos Eléctricos Verticales para obtener información del subsuelo hasta profundidades del orden de los 200 m. Los modelos resistivos obtenidos muestran que hacia el sur del predio, las formaciones geológicas y los acuíferos se profundizan y hacia el oeste, la electroestratigrafía indicaría que hasta los 145 m de profundidad se hallarían sedimentos no consolidados. Por debajo de los mismos habría un resistivo (709 Ohm.m) que podría corresponder a un sedimento consolidado. Se detectaron distintos niveles de acuíferos a profundidades de 5 m y 29 m (acuíferos Pampeano y Puelche) con valores de 19 Ohm.m a 245 Ohm.m respectivamente. Y niveles de acuícludos, acuitardos y aún acuíferos más profundos (Formaciones Paraná y Olivos) hasta los 127m de profundidad con resistividades de 0,8 Ohm.m a 212 Ohm.metro

Topological and Universal Aspects of Bosonized Interacting Fermionic Systems in (2+1)d

General results on the structure of the bosonization of fermionic systems in $(2+1)$d are obtained. In particular, the universal character of the bosonized topological current is established and applied to generic fermionic current interactions. The final form of the bosonized action is shown to be given by the sum of two terms. The first one corresponds to the bosonization of the free fermionic action and turns out to be cast in the form of a pure Chern-Simons term, up to a suitable nonlinear field redefinition. We show that the second term, following from the bosonization of the interactions, can be obtained by simply replacing the fermionic current by the corresponding bosonized expression.Comment: 29 pages, RevTe

Características morfo-arquitecturales y fenológicas de Ugni molinae (Myrtaceae): una especie arbustiva andino-patagónica con frutos comestibles

Background and aims: Ugni molinae (Myrtaceae) is a shrub species native to southern Chile − where it is known as “murta” or “murtilla” − and Argentina. This study was aimed at providing morpho-architectural information about U. molinae so as to promote its cultivation and introduction in productive systems of Argentina. M&M: Observations of U. molinae were performed at different scales (plants, foliated axes and annual shoots) for plants developed in natural populations and plants derived from seeds and stem cuttings sampled at the Lago Puelo National Park and its surroundings (Chubut province, Argentina) and grown in nurseries for five years. Results: Short annual shoots of U. molinae complete their extension without branching, whereas long annual shoots may, as they extend, develop branches from intermediate and/or distal nodes. Flowering may start from the second or third year after seed germination or cut rooting. Most flowers develop at the end of spring from basal nodes of growing shoots. Plant structure changes from a clearly hierarchical to a non-hierarchical architecture in the first years of growth.  Conclusions: Ugni molinae may be multiplied easily from stem cuttings and seed germination. A short internode and small green leaves associated with it are clear markers of a limit between two successive annual shoots. More detailed studies about the development and productivity of this species in Argentina are necessary in order to evaluate the factibility of its inclusion in productive systems.Introducción y objetivos: Ugni molinae (Myrtaceae) es una especie arbustiva nativa del sur de Chile − donde se la conoce como “murta” o “murtilla” − y de Argentina. Este estudio tiene como objetivo aportar información morfo-arquitectural de U. molinae, y así promover su cultivo e introducción en sistemas productivos de Argentina. M&M: Se realizaron observaciones de U. molinae a diferentes niveles (planta completa, ejes y brotes anuales) sobre plantas desarrolladas en poblaciones naturales y plantas derivadas de semillas o de enraizamiento de estacas y mantenidas en viveros por cinco años. Resultados: Los brotes cortos de U. molinae completan su extensión sin ramificarse, mientras que los brotes de mayor longitud pueden ramificarse durante su alargamiento a partir de nudos intermedios y/o distales. El inicio de la floración se produce a partir del segundo al tercer año desde la germinación de una semilla o del enraizamiento de una estaca. La mayoría de las flores se forman a fines de la primavera a partir de nudos basales de brotes en alargamiento. La arquitectura de las plantas cambia desde claramente jerárquica a no-jerárquica en los primeros años de desarrollo.  Conclusiones: Ugni molinae puede multiplicarse con facilidad a partir del enraizamiento de estacas o de germinación de semillas. El desarrollo de un entrenudo corto asociado a hojas verdes pequeñas es un claro indicador del límite entre brotes anuales sucesivos. Se necesitan estudios más detallados acerca del desarrollo y la productividad de esta especie en la Argentina para evaluar su inclusión en sistemas productivos

The Initial-Final Mass Relation among White Dwarfs in Wide Binaries

We present the initial-final mass relation derived from 10 white dwarfs in wide binaries that consist of a main sequence star and a white dwarf. The temperature and gravity of each white dwarf was measured by fitting theoretical model atmospheres to the observed spectrum using a $\chi^{2}$ fitting algorithm. The cooling time and mass was obtained using theoretical cooling tracks. The total age of each binary was estimated from the chromospheric activity of its main sequence component to an uncertainty of about 0.17 dex in log \textit{t} The difference between the total age and white dwarf cooling time is taken as the main sequence lifetime of each white dwarf. The initial mass of each white dwarf was then determined using stellar evolution tracks with a corresponding metallicity derived from spectra of their main sequence companions, thus yielding the initial-final mass relation. Most of the initial masses of the white dwarf components are between 1 - 2 M$_{\odot}$. Our results suggest a correlation between the metallicity of a white dwarf's progenitor and the amount of post-main-sequence mass loss it experiences - at least among progenitors with masses in the range of 1 - 2 M$_{\odot}$. A comparison of our observations to theoretical models suggests that low mass stars preferentially lose mass on the red giant branch.Comment: 28 pages, 8 figures, accepted for publication in Ap