3,918 research outputs found
Transition amplitude, partition function and the role of physical degrees of freedom in gauge theories
This work explores the quantum dynamics of the interaction between scalar
(matter) and vectorial (intermediate) particles and studies their thermodynamic
equilibrium in the grand-canonical ensemble. The aim of the article is to
clarify the connection between the physical degrees of freedom of a theory in
both the quantization process and the description of the thermodynamic
equilibrium, in which we see an intimate connection between physical degrees of
freedom, Gibbs free energy and the equipartition theorem. We have split the
work into two sections. First, we analyze the quantum interaction in the
context of the generalized scalar Duffin-Kemmer-Petiau quantum electrodynamics
(GSDKP) by using the functional formalism. We build the Hamiltonian structure
following the Dirac methodology, apply the Faddeev-Senjanovic procedure to
obtain the transition amplitude in the generalized Coulomb gauge and, finally,
use the Faddeev-Popov-DeWitt method to write the amplitude in covariant form in
the no-mixing gauge. Subsequently, we exclusively use the Matsubara-Fradkin
(MF) formalism in order to describe fields in thermodynamical equilibrium. The
corresponding equations in thermodynamic equilibrium for the scalar, vectorial
and ghost sectors are explicitly constructed from which the extraction of the
partition function is straightforward. It is in the construction of the
vectorial sector that the emergence and importance of the ghost fields are
revealed: they eliminate the extra non-physical degrees of freedom of the
vectorial sector thus maintaining the physical degrees of freedom
Causal Theory for the Gauged Thirring Model
We consider the (2+1)-dimensional massive Thirring model as a gauge theory,
with one fermion flavor, in the framework of the causal perturbation theory and
address the problem of dynamical mass generation for the gauge boson. In this
context we get an unambiguous expression for the coefficient of the induced
Chern-Simons term.Comment: LaTex, 21 pages, no figure
Radiative Corrections for the Gauged Thirring Model in Causal Perturbation Theory
We evaluate the one-loop fermion self-energy for the gauged Thirring model in
(2+1) dimensions, with one massive fermion flavor, in the framework of the
causal perturbation theory. In contrast to QED, the corresponding two-point
function turns out to be infrared finite on the mass shell. Then, by means of a
Ward identity, we derive the on-shell vertex correction and discuss the role
played by causality for nonrenormalizable theories.Comment: LaTex, 09 pages, no figures. Title changed and introduction enlarged.
To be published in Eur. Phys. J.
Gauged Thirring Model in the Heisenberg Picture
We consider the (2+1)-dimensional gauged Thirring model in the Heisenberg
picture. In this context we evaluate the vacuum polarization tensor as well as
the corrected gauge boson propagator and address the issues of generation of
mass and dynamics for the gauge boson (in the limits of QED and Thirring
model as a gauge theory, respectively) due to the radiative corrections.Comment: 14 pages, LaTex, no figure
The impact of EFQM awards on organizational management
Purpose: The purpose of this paper is to examine how the recognition of the European Foundation for Quality and Management (EFQM) awards to organizations (variable 1), particularly contribute to the improvement of management models, translated into different stages of evolution of management models/management control systems (variable 2), testing the hypothesis of correlation between these two variables.
Methodology: The investigation covers the 35 organizations that won EFQM awards in Portugal (2010-2015). The bases are the different levels/scores of EFQM awards. Additionally, a questionnaire was used regarding the different stages of management models/management control systems (1=Basic stage of management control systems; 10=Advanced and very efficient management control systems stage). Moreover, interviews in all 35 organizations implied the collection of more accurate data.
Findings: Important findings result from the research. Whenever organizations implement a quality management process/EFQM, substantial improvements occur in organizations regarding the implementation of management control models. Additionally, a positive and very strong correlation was found between the two variables: (i) different levels/scores of EFQM awards, and (ii) results of the questionnaire on different stages of management models/management control systems.
Practical implications: The study makes it possible to conclude that the more an organization invests in a quality management process/program, the more efficient and useful a management control model becomes.
Originality/Value: There is a gap in literature regarding the impact of quality management on the effectiveness of management models. Our study helps to close this gap, contributing to the development of a new body of knowledge, by assessing this favourable impact.info:eu-repo/semantics/publishedVersio
Remarks on Infrared Dynamics in QED3
In this work we study how the infrared sector of the interaction Hamiltonian
can affect the construction of the S matrix operator of QED in (2+1)
dimensions.Comment: 9 page
Tuberculosis Prevalence in Children at High-Risk from Ameixoeira, Lisbon
Introdução. As taxas de prevalĂȘncia de tuberculose infecção e doença tĂȘm declinado em Portugal. No entanto, a pandemia
da infecção pelo vĂrus de imunodeficiĂȘncia humana, a toxicodependĂȘncia e mĂĄs condiçÔes de salubridade podem reverter esta tendĂȘncia. O rastreio de crianças assintomĂĄticas em contacto com adultos em risco de contrair a doença Ă© crucial pois
os casos de tuberculose infantil sĂŁo devidos a um risco elevado e recente de transmissĂŁo na comunidade.
Objectivos. Determinar a prevalĂȘncia de tuberculose infecção/doença numa amostra de crianças em contacto com adultos de risco; determinar a prevalĂȘncia de factores de risco
e sua efectividade como preditores de infecção/doença nesta amostra; administrar quimioprofilaxia/terapĂȘutica aos casos
detectados e investigar as possĂveis fontes de contĂĄgio.
População e MĂ©todos. Estudou-se uma amostra de conveniĂȘncia de crianças que frequentavam uma instituição recreativa para crianças e jovens na Ameixoeira â Lumiar (Lisboa)
no perĂodo de Abril-Maio de 2005. Aplicou-se um questionĂĄrio sobre factores de risco para tuberculose e fez-se prova tuberculĂnica pelo mĂ©todo de Mantoux. A leitura foi efectuada apĂłs 72 horas. Os casos positivos (induração > 15 mm de diĂąmetro) foram submetidos a avaliação clĂnica e radiolĂłgica
e quimioprofilaxia/terapĂȘutica. Os seus coabitantes foram investigados. Os dados foram analisados pelo programa StatCal-Epiinfo 3.2.2.
Resultados. Estudaram-se 100 crianças (54 famĂlias) das quais 44% tinham pelo menos um factor de risco. Em duas crianças o teste de tuberculina foi positivo sendo o diagnĂłstico
final de tuberculose infecção. O rastreio dos seus coabitantes foi negativo. AprevalĂȘncia de infecção na amostra
estudada foi de 2:100. O questionĂĄrio aplicado teve um valor preditivo positivo de 2,2% e negativo de 98% para detectar infecção por tuberculose. ConclusĂ”es. A prevalĂȘncia de infecção na amostra de crianças estudada foi elevada. O questionĂĄrio aplicado teve pouca acuidade para predizer a presença de infecção/doença nesta amostra
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