Linear response theory in asymmetric nuclear matter for Skyrme functionals including spin-orbit and tensor terms

The formalism of linear response theory for a Skyrme functional including spin-orbit and tensor terms is generalized to the case of infinite nuclear matter with arbitrary isospin asymmetry. Response functions are obtained by solving an algebraic system of equations, which is explicitly given. Spin-isospin strength functions are analyzed varying the conditions of density, momentum transfer, asymmetry, and temperature. The presence of instabilities, including the spinodal one, is studied by means of the static susceptibility

Linear response of homogeneous nuclear matter with energy density functionals

Response functions of infinite nuclear matter with arbitrary isospin asymmetry are studied in the framework of the random phase approximation. The residual interaction is derived from a general nuclear Skyrme energy density functional. Besides the usual central, spin-orbit and tensor terms it could also include other components as new density-dependent terms or three-body terms. Algebraic expressions for the response functions are obtained from the Bethe-Salpeter equation for the particle-hole propagator. Applications to symmetric nuclear matter, pure neutron matter and asymmetric nuclear matter are presented and discussed. Spin-isospin strength functions are analyzed for varying conditions of density, momentum transfer, isospin asymmetry, and temperature for some representative Skyrme functionals. Particular attention is paid to the discussion of instabilities, either real or unphysical, which could manifest in finite nuclei

Structure and Stability of 3He Droplets

We have studied the structure of 3He droplets at zero temperature using a density functional approach plus a configuration interaction calculation in an harmonic oscillator major shell. The most salient feature of open shell drops is that the valence atoms couple their spins to the maximum value compatible with Pauli's principle, building a large magnetic moment. We have determined that 29 atoms constitute the smallest self-bound droplet

Errores conceptuales en los modelos atómicos cuánticos

SUMMARY We analyze how the basic concepts about atomic models are introduced into the Spanish educational system. We considered the textbooks most currently used in the educational levels from 8th EGB to the 1st University level. We finally discuss the possible sources of misconceptions

Magic numbers, excitation levels, and other properties of small neutral math clusters (N < 50)

The ground-state energies and the radial and pair distribution functions of neutral math clusters are systematically calculated by the diffusion Monte Carlo method in steps of one math atom from 3 to 50 atoms. In addition the chemical potential and the low-lying excitation levels of each cluster are determined with high precision. These calculations reveal that the “magic numbers” observed in experimental math cluster size distributions, measured for free jet gas expansions by nondestructive matter-wave diffraction, are not caused by enhanced stabilities. Instead they are explained in terms of an enhanced growth due to sharp peaks in the equilibrium concentrations in the early part of the expansion. These peaks appear at cluster sizes which can just accommodate one more additional stable excitation. The good agreement with experiment provides not only experimental confirmation of the energy level and the chemical potential calculations, but also evidence for a new mechanism which can lead to magic numbers in cluster size distributions. By accounting for the falloff of the radial density distributions at the surface and a size-dependent surface tension, the energy levels are demonstrated to be consistent with a modified Rayleigh model of surface excitations. The compressibility coefficient of these small clusters is found to be one order of magnitude smaller than the bulk [email protected]

Obtencion de recubrimientos autolubricados por proyeccion termica de plasma atmosferico (APS) como alternativa a los lubricantes liquidos

La obtención de recubrimientos con bajos coeficientes de fricción, es una innovadora respuesta a la creciente demanda industrial de alternativas para los tradicionales sistemas lubricados con aceites. Para este fin, la introducción de un sólido lubricante, en una matriz con buenas propiedades mecánicas, ha de conferir al conjunto un bajo coeficiente de fricción y mejorar la resistencia al desgaste del recubrimiento, favoreciendo además, la utilización a elevadas temperaturas, en las que los lubricantes líquidos convencionales presentan limitaciones. En el Centro de Proyección Térmica (CPT) de la Universidad de Barcelona se han obtenido mediante proyección de Plasma Atmosférico (APS) recubrimientos autolubricados de Ni-Grafito y Cr2O3-CaF2, estudiando con especial interés las propiedades y el efecto que produce el grafito y el CaF2 en las matrices metálica y cerámica respectivamente. Se ha determinado en los dos casos que el desgaste originado en los recubrimientos es bajo, si bien los coeficientes de fricción varían ostensiblemente en función del sistema indicado. Los resultados obtenidos indican que el recubrimiento de Ni-Grafito posee un comportamiento idóneo capaz de competir con los tradicionales lubricantes líquidos

Derives místiques de la física quàntica

I Curs de La ciéncia pren la paraula; els problemes socials de la pseudociéncia (2013

Energetics and structure of small para-hydrogen clusters

5 pages, 3 figures.-- PACS nrs.: 67.40.Db; 36.40.-c; 61.46.Bc.-- ISI Article Identifier: 000248052200063Printed version published on Sep 2007.Quantum diffusion Monte Carlo simulations have been performed to systematically analyze the energetics and structure of (p_H2)(N) clusters with N = 3-50 molecules, with the aim of finding signals of magic sizes and discerning the cluster structure. The analysis of the calculated chemical potential as a function of N provides a definitive confirmation of the magic size N=13. The calculations show that (p_H2)(N) clusters exhibit a clear geometrical order, which excludes considering them as liquid droplets.This work was supported by MCyT (Spain), grant No. FIS2004-0912.Peer reviewe

Energetics and structure of small para-hydrogen clusters

5 pages, 3 figures.-- PACS nrs.: 67.40.Db; 36.40.-c; 61.46.Bc.-- ISI Article Identifier: 000248052200063Printed version published on Sep 2007.Quantum diffusion Monte Carlo simulations have been performed to systematically analyze the energetics and structure of (p_H2)(N) clusters with N = 3-50 molecules, with the aim of finding signals of magic sizes and discerning the cluster structure. The analysis of the calculated chemical potential as a function of N provides a definitive confirmation of the magic size N=13. The calculations show that (p_H2)(N) clusters exhibit a clear geometrical order, which excludes considering them as liquid droplets.This work was supported by MCyT (Spain), grant No. FIS2004-0912.Peer reviewe

Física moderna

Existe otra edición de 1990Material de trabajo para facilitar la labor de los profesores de física en el 2º curso de los bachilleratos de ciencias naturales y técnico industrial. Se organiza en torno a un conjunto de actividades que se plantean a los alumnos. Constan de una introducción, la actividad en sí misma y sugerencias y comentarios. Al final de cada tema se incluyen comentarios para el profesor sobre aspectos didácticos, bibliográficos, etc.ValenciaBiblioteca de Educación del Ministerio de Educación, Cultura y Deporte; Calle San Agustín 5 -3 Planta; 28014 Madrid; Tel. +34917748000; [email protected]