5,596 research outputs found
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
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
Quantum gauge boson propagators in the light front
Gauge fields in the light front are traditionally addressed via the
employment of an algebraic condition in the Lagrangian density,
where is the gauge field (Abelian or non-Abelian) and is the
external, light-like, constant vector which defines the gauge proper. However,
this condition though necessary is not sufficient to fix the gauge completely;
there still remains a residual gauge freedom that must be addressed
appropriately. To do this, we need to define the condition with . The implementation of this
condition in the theory gives rise to a gauge boson propagator (in momentum
space) leading to conspicuous non-local singularities of the type where . These singularities must be conveniently
treated, and by convenient we mean not only matemathically well-defined but
physically sound and meaningfull as well. In calculating such a propagator for
one and two noncovariant gauge bosons those singularities demand from the
outset the use of a prescription such as the Mandelstam-Leibbrandt (ML) one. We
show that the implementation of the ML prescription does not remove certain
pathologies associated with zero modes. However we present a causal,
singularity-softening prescription and show how to keep causality from being
broken without the zero mode nuisance and letting only the propagation of
physical degrees of freedom.Comment: 10 page
Schwinger's Principle and Gauge Fixing in the Free Electromagnetic Field
A manifestly covariant treatment of the free quantum eletromagnetic field, in
a linear covariant gauge, is implemented employing the Schwinger's Variational
Principle and the B-field formalism. It is also discussed the abelian Proca's
model as an example of a system without constraints.Comment: 8 pages. Format PTPtex. No figur
Cosmological Bianchi Class A models in S\'aez-Ballester theory
We use the S\'aez-Ballester (SB) theory on anisotropic Bianchi Class A
cosmological model, with barotropic fluid and cosmological constant, using the
Hamilton or Hamilton-Jacobi approach. Contrary to claims in the specialized
literature, it is shown that the S\'aez-Ballester theory cannot provide a
realistic solution to the dark matter problem of Cosmology for the dust epoch,
without a fine tunning because the contribution of the scalar field in this
theory is equivalent to a stiff fluid (as can be seen from the energy--momentum
tensor for the scalar field), that evolves in a different way as the dust
component. To have similar contributions of the scalar component and the dust
component implies that their past values were fine tunned. So, we
reinterpreting this null result as an indication that dark matter plays a
central role in the formation of structures and galaxy evolution, having
measureable effects in the cosmic microwave bound radiation, and than this
formalism yield to this epoch as primigenius results. We do the mention that
this formalism was used recently in the so called K-essence theory applied to
dark energy problem, in place to the dark matter problem. Also, we include a
quantization procedure of the theory which can be simplified by reinterpreting
the theory in the Einstein frame, where the scalar field can be interpreted as
part of the matter content of the theory, and exact solutions to the
Wheeler-DeWitt equation are found, employing the Bianchi Class A cosmological
models.Comment: 24 pages; ISBN: 978-953-307-626-3, InTec
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