306 research outputs found
Modified Laplace transformation method at finite temperature: application to infra-red problems of N component theory
Modified Laplace transformation method is applied to N component
theory and the finite temperature problem in the massless limit is re-examined
in the large N limit. We perform perturbation expansion of the dressed thermal
mass in the massive case to several orders and try the massless approximation
with the help of modified Laplace transformation. The contribution with
fractional power of the coupling constant is recovered from the truncated
massive series. The use of inverse Laplace transformation with respect to the
mass square is crucial in evaluating the coefficients of fractional power
terms.Comment: 16pages, Latex, typographical errors are correcte
The Pressure of Hot Theory at order
The order contribution to the pressure of massless theory
at nonzero temperature is obtained explicitly. Lower order contributions are
reconsidered and two issues leading to the optimal choice of rearranged
Lagrangian for such calculations are clarified.Comment: 15 pages, Latex, postscript file attached at the en
Effective Field Theory Approach to High-Temperature Thermodynamics
An effective field theory approach is developed for calculating the
thermodynamic properties of a field theory at high temperature and weak
coupling . The effective theory is the 3-dimensional field theory obtained
by dimensional reduction to the bosonic zero-frequency modes. The parameters of
the effective theory can be calculated as perturbation series in the running
coupling constant . The free energy is separated into the contributions
from the momentum scales and , respectively. The first term can be
written as a perturbation series in . If all forces are screened at the
scale , the second term can be calculated as a perturbation series in
beginning at order . The parameters of the effective theory satisfy
renormalization group equations that can be used to sum up leading logarithms
of . We apply this method to a massless scalar field with a
interaction, calculating the free energy to order and the
screening mass to order .Comment: 40 pages, LaTeX, 5 uuecoded figure
The Three-Loop Free Energy for High-Temperature QED and QCD with Fermions
We compute the free energy density for gauge theories, with fermions, at high
temperature and zero chemical potential. Specifically, we analytically compute
the free energy through , which requires the evaluation of three-loop
diagrams. This computation extends our previous result for pure gauge QCD.Comment: 26 pages, 9 postscript figures, UW/PT-94-1
The Free Energy Of Hot Gauge Theories
The total perturbative contribution to the free-energy of hot SU(3) gauge
theory is argued to lie significantly higher than the full result obtained by
lattice simulations. This then suggests the existence of large non-perturbative
corrections even at temperatures a few times above the critical temperature.
Some speculations are then made on the nature and origin of the
non-perturbative corrections. The analysis is then carried out for quantum
chromodynamics, gauge theories, and quantum electrodynamics, leading
to a conjecture and one more speculation.Comment: Revised Journal version;25 pages Latex and 11 .eps figures in
separate file. Requires epsf.st
On the screening of static electromagnetic fields in hot QED plasmas
We study the screening of static magnetic and electric fields in massless
quantum electrodynamics (QED) and massless scalar electrodynamics (SQED) at
temperature . Various exact relations for the static polarisation tensor are
first reviewed and then verified perturbatively to fifth order (in the
coupling) in QED and fourth order in SQED, using different resummation
techniques. The magnetic and electric screening masses squared, as defined
through the pole of the static propagators, are also calculated to fifth order
in QED and fourth order in SQED, and their gauge-independence and
renormalisation-group invariance is checked. Finally, we provide arguments for
the vanishing of the magnetic mass to all orders in perturbation theory.Comment: 37 pages, 8 figure
Solution to the 3-loop -derivable Approximation for Scalar Thermodynamics
We solve the 3-loop -derivable approximation to the thermodynamics of
the massless field theory by reducing it to a 1-parameter variational
problem. The thermodynamic potential is expanded in powers of and ,
where is the coupling constant, is a variational mass parameter, and
is the temperature. There are ultraviolet divergences beginning at 6th
order in that cannot be removed by renormalization. However the finite
thermodynamic potential obtained by truncating after terms of 5th order in
and defines a stable approximation to the thermodynamic functions.Comment: 4 pages, 1 figur
Solution to the 3-Loop -Derivable Approximation for Massless Scalar Thermodynamics
We develop a systematic method for solving the 3-loop -derivable
approximation to the thermodynamics of the massless field theory. The
method involves expanding sum-integrals in powers of and m/T, where g is
the coupling constant, m is a variational mass parameter, and T is the
temperature. The problem is reduced to one with the single variational
parameter m by solving the variational equations order-by-order in and
m/T. At the variational point, there are ultraviolet divergences of order
that cannot be removed by any renormalization of the coupling constant. We
define a finite thermodynamic potential by truncating at order in g
and m/T. The associated thermodynamic functions seem to be perturbatively
stable and insensitive to variations in the renormalization scale.Comment: 57 pages, 10 figure
The Free Energy of High Temperature QED to Order From Effective Field Theory
Massless quantum electrodynamics is studied at high temperature and zero
chemical potential. We compute the Debye screening mass to order and
the free energy to order } by an effective field theory approach,
recently developed by Braaten and Nieto. Our results are in agreement with
calculations done in resummed perturbation theory. This method makes it
possible to separate contributions to the free energy from different momentum
scales (order and ) and provides an economical alternative to
computations in the full theory which involves the dressing of internal
propagators.Comment: 10 pages Latex, 6 figure
- …