6,301 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
Variational Formulation for Quaternionic Quantum Mechanics
A quaternionic version of Quantum Mechanics is constructed using the
Schwinger's formulation based on measurements and a Variational Principle.
Commutation relations and evolution equations are provided, and the results are
compared with other formulations.Comment: Talk given at ICCA*, May 26-30 of 2008, Campinas, SP, Brazil. 18
pages, no figur
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
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
Quantum State Density and Critical Temperature in M-theory
We discuss the asymptotic properties of quantum states density for
fundamental branes which can yield a microscopic interpretation of the
thermodynamic quantities in M-theory. The matching of BPS part of spectrum for
superstring and supermembrane gives the possibility of getting membrane's
results via string calculations. In the weak coupling limit of M-theory the
critical behavior coincides with the first order phase transition in standard
string theory at temperature less than the Hagedorn's temperature . The
critical temperature at large coupling constant is computed by considering
M-theory on manifold with topology .
Alternatively we argue that any finite temperature can be introduced in the
framework of membrane thermodynamics.Comment: 16 pages, published in Mod. Phys. Lett. A16(2001)224
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