4,751 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.
Axial Anomaly through Analytic Regularization
In this work we consider the 2-point Green's functions in (1+1) dimensional
quantum electrodynamics and show that the correct implementation of analytic
regularization gives a gauge invariant result for the vaccum polarization
amplitude and the correct coefficient for the axial anomaly.Comment: 8 pages, LaTeX, no figure
Causal Propagators for Algebraic Gauges
Applying the principle of analytic extension for generalized functions we
derive causal propagators for algebraic non-covariant gauges. The so generated
manifestly causal gluon propagator in the light-cone gauge is used to evaluate
two one-loop Feynman integrals which appear in the computation of the
three-gluon vertex correction. The result is in agreement with that obtained
through the usual prescriptions.Comment: LaTex, 09 pages, no figure
Bianchi Type I Cosmology in N=2, D=5 Supergravity
The dynamics and evolution of Bianchi type I space-times is considered in the
framework of the four-dimensional truncation of a reduced theory obtained from
the N=2,D=5 supergravity. The general solution of the gravitational field
equations can be represented in an exact parametric form. All solutions have a
singular behavior at the initial/final moment, except when the space-time
geometry reduces to the isotropic flat case. Generically the obtained
cosmological models describe an anisotropic, expanding or collapsing, singular
Universe with a non-inflationary evolution for all times.Comment: revised version to appear in PR
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
Cylindrically symmetric, static strings with a cosmological constant in Brans-Dicke theory
The static, cylindrically symmetric vacuum solutions with a cosmological
constant in the framework of the Brans-Dicke theory are investigated. Some of
these solutions admitting Lorentz boost invariance along the symmetry axis
correspond to local, straight cosmic strings with a cosmological constant. Some
physical properties of such solutions are studied. These strings apply
attractive or repulsive forces on the test particles. A smooth matching is also
performed with a recently introduced interior thick string solution with a
cosmological constant.Comment: 8 pages, Revtex; Published versio
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