4,579 research outputs found
A Note on Supersymmetric WZW term in Four Dimensions
We reconsider the supersymmetric Wess-Zumino-Witten (SWZW) term in four
dimensions. It has been known that the manifestly supersymmetric form of the
SWZW term includes derivative terms on auxiliary fields, the highest components
of chiral superfields, and then we cannot eliminate them by their equations of
motion. We discuss a possibility for the elimination of such derivative terms
by adding total derivative terms. Although the most of derivative terms can be
eliminated as in this way, we find that all the derivative terms can be
canceled, if and only if an anomalous term in SWZW term vanishes. As a
byproduct, we find the first example of a higher derivative term free from such
a problem.Comment: LaTeX, 10 pages, no figures, typos corrected, references added,
accepted for publication in Modern Physics Letters
SDSS White Dwarf mass distribution at low effective temperatures
The DA white dwarfs in the Sloan Digital Sky Survey, as analyzed in the
papers for Data Releases 1 and 4, show an increase in surface gravity towards
lower effective temperatures below 11500 K. We study the various possible
explanations of this effect, from a real increase of the masses to
uncertainties or deficiencies of the atmospheric models. No definite answer is
found but the tentative conclusion is that it is most likely the current
description of convection in the framework of the mixing-length approximation,
which leads to this effect.Comment: to appear in the proceedings of the 16th European Workshop on White
Dwarfs, Barcelona, 200
Charged Particle Dynamics in the Field of a Slowly Rotating Compact Star
We study the dynamics of a charged particle in the field of a slowly rotating
compact star in the gravitoelectromagnetic approximation to the geodesic
equation . The star is assumed to be surrounded by an ideal, highly conducting
plasma (taken as a magnetohydrodynamic fluid) with a stationary, axially
symmetric electromagnetic field. The general relativistic Maxwell equations are
solved to obtain the effects of the background spacetime on the electromagnetic
field in the linearized Kerr spacetime. The equations of motion are then set up
and solved numerically to incorporate the gravitational as well as the
electromagnetic effects. The analysis shows that in the slow rotation
approximation the frame dragging effects on the electromagnetic field are
absent. However the particle is directly effected by the rotating gravitational
source such that close to the star the gravitational and electromagnetic field
produce contrary effects on the particle's trajectory.Comment: 10 pages, 6 figures in B & W PostScript Forma
Slow shocks and conduction fronts from Petschek reconnection of skewed magnetic fields: two-fluid effects
In models of fast magnetic reconnection, flux transfer occurs within a small
portion of a current sheet triggering stored magnetic energy to be thermalized
by shocks. When the initial current sheet separates magnetic fields which are
not perfectly anti-parallel, i.e. they are skewed, magnetic energy is first
converted to bulk kinetic energy and then thermalized in slow magnetosonic
shocks. We show that the latter resemble parallel shocks or hydrodynamic shocks
for all skew angles except those very near the anti-parallel limit. As for
parallel shocks, the structures of reconnection-driven slow shocks are best
studied using two-fluid equations in which ions and electrons have independent
temperature. Time-dependent solutions of these equations can be used to predict
and understand the shocks from reconnection of skewed magnetic fields. The
results differ from those found using a single-fluid model such as
magnetohydrodynamics. In the two-fluid model electrons are heated indirectly
and thus carry a heat flux always well below the free-streaming limit. The
viscous stress of the ions is, however, typically near the fluid-treatable
limit. We find that for a wide range of skew angles and small plasma beta an
electron conduction front extends ahead of the slow shock but remains within
the outflow jet. In such cases conduction will play a more limited role in
driving chromospheric evaporation than has been predicted based on
single-fluid, anti-parallel models
Cool White Dwarfs Found in the UKIRT Infrared Deep Sky Survey
We present the results of a search for cool white dwarfs in the United
Kingdom InfraRed Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) Large Area
Survey (LAS). The UKIDSS LAS photometry was paired with the Sloan Digital Sky
Survey (SDSS) to identify cool hydrogen-rich white dwarf candidates by their
neutral optical colors and blue near-infrared colors, as well as faint Reduced
Proper Motion magnitudes. Optical spectroscopy was obtained at Gemini
Observatory, and showed the majority of the candidates to be newly identified
cool degenerates, with a small number of G- to K-type (sub)dwarf contaminants.
Our initial search of 280 deg2 of sky resulted in seven new white dwarfs with
effective temperature T_eff ~ 6000 K. The current followup of 1400 deg2 of sky
has produced thirteen new white dwarfs. Model fits to the photometry show that
seven of the newly identified white dwarfs have 4120 K <= T_eff <= 4480 K, and
cooling ages between 7.3 Gyr and 8.7 Gyr; they have 40 km/s <= v_tan <= 85 km/s
and are likely to be thick disk 10-11 Gyr-old objects. The other half of the
sample has 4610 K <= T_eff <= 5260 K, cooling ages between 4.3 Gyr and 6.9 Gyr,
and 60 km/s <= v_tan <= 100 km/s. These are either thin disk remnants with
unusually high velocities, or lower-mass remnants of thick disk or halo late-F
or G stars.Comment: To appear in ApJ, accepted April 18 2011. 34 pages include 11 Figures
and 5 Table
Oscillating p-Branes
Coset methods are used to construct the action describing the dynamics
associated with the spontaneous breaking of the Poincare symmetries of D
dimensional space-time due to the embedding of a p-brane with codimension
N=D-p-1. The resulting world volume action is an ISO(1,p+N) invariant
generalization of the Nambu-Goto action in d=p+1 dimensional space-time.
Analogous results are obtained for an AdS p-brane with codimension N embedded
in D dimensional AdS space, yielding an SO(2,p+N) invariant version of the
Nambu-Goto action in d=p+1 dimensional space-time. Attention is focused on a
supersymmetric extension of the D=6 Minkowski space case with an embedded p=3
brane; a particular realization of which is provided by a non-BPS vortex. Here
both the Nambu-Goto-Akulov-Volkov action and its dual tensor form are
presented.Comment: 25 pages, no figure
Amplification profiles of the SSR markers in cultivars of hexaploid wheat and their relatives
Dissertação de Mestrado em Psicologia das Organizações e do Trabalho, apresentada à Faculdade de Psicologia e de Ciências da Educação da Universidade de CoimbraEsta investigação insere-se na linha de investigação ligada à
abordagem dos stakeholders e teve como principal objectivo estudar as
relações existentes entre os padrões discursivos adoptados pela gestão (o
discurso financeiro e económico, o discurso da responsabilidade social da
empresa e o discurso dos stakeholders) e a saliência atribuída aos quatro
tipos de stakeholders considerados neste estudo (sócios/accionistas, clientes,
colaboradores e comunidade). Procurámos, ainda, analisar se determinadas
características organizacionais e dos gestores influenciavam os seus
discursos, e investigámos a possibilidade de haver um efeito moderador do
Ciclo de Vida das Organizações (CVO) na relação entre os discursos
adoptados pelos gestores e a saliência atribuída aos diferentes stakeholders
organizacionais. Neste sentido, foi utilizada uma amostra de 111 gestores,
provenientes de 50 empresas de várias dimensões e sectores,
maioritariamente da zona centro do país, que responderam a três
questionários: Questionário da Gestão de Stakeholders (GS) de Carvalho
(2007); Questionário das Preocupações e Prioridades da Gestão de Carvalho
(2007); e, Questionário do Ciclo de Vida Organizacional (CVO) de Carvalho
(2001). Os resultados encontrados sugerem que, apesar de se verificarem
algumas relações significativas entre estas três variáveis em estudo, não se
verificou, tal como previsto, que a variável CVO moderasse a relação entre
os discursos dos gestores e a saliência dos stakeholders. As implicações
teóricas e práticas destes resultados serão alvo de análise e de discussão.This research falls in the line of research related to the stakeholder
approach and had a main objective to study the relationship between the
predominant speech patterns adopted by management (the financial and
economic discourse, the discourse of corporate social responsibility and the
discourse of stakeholders) and the salience attributed to four types of
stakeholders considered in this study (partners / shareholders, clients,
employees and community).
We also tried to test whether certain organizational and managerial
characteristics influenced their speeches, and investigated the possibility of a
moderating effect of the CVO in the relationship between the organizational
discourses adopted by managers and the salience attributed to the different
stakeholders. In this sense, we used a sample of 111 managers, from 50
companies of various sizes and sectors, mostly in the center of the country
who responded to three questionnaires: Questionnaire Stakeholder
Management (GS) (Carvalho, 2007); Questionnaire Concerns and Priorities
of Management (Carvalho, 2007); and Questionnaire Organizational Life
Cycle (CVO) (Carvalho, 2001). The results suggest that, despite showing
some significant relationships between these three variables studied, the
variable CVO did not moderate the relationship between discourses of
managers and stakeholders’ salience, as expected. The theoretical and
practical implications of these results will be subject to analysis and
discussion
Brane Vector Phenomenology
Local oscillations of the brane world are manifested as masssive vector
fields. Their coupling to the Standard Model can be obtained using the method
of nonlinear realizations of the spontaneously broken higher dimensional
space-time symmetries, and to an extent, are model independent.
Phenomenological limits on these vector field parameters are obtained using LEP
collider data and dark matter constraints.Comment: 3 pages, 2 figures, late
- …