381 research outputs found
Resummations in Hot Scalar Electrodynamics
The gauge-boson sector of perturbative scalar electrodynamics is investigated
in detail as a testing ground for resummation methods in hot gauge theories. It
also serves as a simple non-trivial reference system for the non-Abelian gluon
plasma. The complete next-to-leading order contributions to the polarization
tensor are obtained within the resummation scheme of Braaten and Pisarski. The
simpler scheme proposed recently by Arnold and Espinosa is shown to apply to
static quantities only, whereas Braaten-Pisarski resummation turns out to need
modification for collective phenomena close to the light-cone. Finally, a
recently proposed resummation of quasi-particle damping contributions is
assessed critically.Comment: 53 p. LaTeX, 7 figs. (2 in LaTeX, 5 EPS appended as uu-encoded file),
ITP-UH-01/94 & DESY 94-03
Effects of weak self-interactions in a relativistic plasma on cosmological perturbations
The exact solutions for linear cosmological perturbations which have been
obtained for collisionless relativistic matter within thermal field theory are
extended to a self-interacting case. The two-loop contributions of scalar
theory to the thermal graviton self-energy are evaluated, which
give the corrections in the perturbation equations. The changes
are found to be perturbative on scales comparable to or larger than the Hubble
horizon, but the determination of the large-time damping behavior of subhorizon
perturbations requires a resummation of thermally induced masses.Comment: 11 pages, REVTEX, 4 postscript figures included by epsf.sty -
expanded version (more details on the resummation of thermal masses which is
required for the late-time damping behaviour
The gravitational polarization tensor of thermal theory
The low-momentum structure of the gravitational polarization tensor of an
ultrarelativistic plasma of scalar particles with interactions
is evaluated in a two-loop calculation up to and including order
. This turns out to require an improved perturbation theory
which resums a local thermal mass term as well as nonlocal hard-thermal-loop
vertices of scalar and gravitational fields.Comment: 15 pages and 6 figures, uu-encoded postscript fil
Soft Thermal Loops in Scalar Quantum Electrodynamics
Scalar QED is used to study approximations in thermal field theory beyond the
Hard Thermal Loop resummation scheme. For this purpose the photon self energy
is calculated for external momenta of the order e^2T using Hard Thermal Loop
resummed Green functions.Comment: 7 pages, REVTEX, 2 PostScript figures, statement about Ref.[10]
correcte
The dynamics of cosmological perturbations in thermal theory
Using a recent thermal-field-theory approach to cosmological perturbations,
the exact solutions that were found for collisionless ultrarelativistic matter
are generalized to include the effects from weak self-interactions in a
model through order . This includes the effects
of a resummation of thermal masses and associated nonlocal gravitational
vertices, thus going far beyond classical kinetic theory. Explicit solutions
for all the scalar, vector, and tensor modes are obtained for a
radiation-dominated Einstein-de Sitter model containing a weakly interacting
scalar plasma with or without the admixture of an independent component of
perfect radiation fluid.Comment: 32 pages, REVTEX, 13 postscript figures included by epsf.st
Color, Spin and Flavor Diffusion in Quark-Gluon Plasmas
In weakly interacting quark-gluon plasmas diffusion of color is found to be
much slower than the diffusion of spin and flavor because color is easily
exchanged by the gluons in the very singular forward scattering processes. If
the infrared divergence is cut off by a magnetic mass, ,
the color diffusion is , a
factor smaller than spin and flavor diffusion. A similar effect is
expected in electroweak plasmas above due to exchanges. The color
conductivity in quark-gluon plasmas and the electrical conductivity in
electroweak plasmas are correspondingly small in relativistic heavy ion
collisions and the very early universe.Comment: 5 pages, no figure
The graviton self-energy in thermal quantum gravity
We show generally that in thermal gravity, the one-particle irreducible
2-point function depends on the choice of the basic graviton fields. We derive
the relevant properties of a physical graviton self-energy, which is
independent of the parametrization of the graviton field. An explicit
expression for the graviton self-energy at high-temperature is given to
one-loop order.Comment: 13 pages, 2 figure
The Radiative Corrections to the Mass of the Kink Using an Alternative Renormalization Program
In this paper we compute the radiative correction to the mass of the kink in
theory in 1+1 dimensions, using an alternative renormalization
program. In this newly proposed renormalization program the breaking of the
translational invariance and the topological nature of the problem, due to the
presence of the kink, is automatically taken into account. This will naturally
lead to uniquely defined position dependent counterterms. We use the mode
number cutoff in conjunction with the above program to compute the mass of the
kink up to and including the next to the leading order quantum correction. We
discuss the differences between the results of this procedure and the
previously reported ones.Comment: 8 pages, 2 figures. arXiv admin note: substantial text overlap with
arXiv:0806.036
Central charge and renormalization in supersymmetric theories with vortices
Some quantum features of vortices in supersymmetric theories in 1+2
dimensions are studied in a manifestly supersymmetric setting of the superfield
formalism. A close examination of the supercurrent that accommodates the
central charge and super-Poincare charges in a supermultiplet reveals that
there is no genuine quantum anomaly in the supertrace identity and in the
supercharge algebra, with the central-charge operator given by the bare
Fayet-Iliopoulos term alone. The central charge and the vortex spectrum undergo
renormalization on taking the expectation value of the central-charge operator.
It is shown that the vortex spectrum is exactly determined at one loop while
the spectrum of the elementary excitations receives higher-order corrections.Comment: 9 pages, revte
Comment on ``High Temperature Fermion Propagator -- Resummation and Gauge Dependence of the Damping Rate''
Baier et al. have reported the damping rate of long-wavelength fermionic
excitations in high-temperature QED and QCD to be gauge-fixing-dependent even
within the resummation scheme due to Braaten and Pisarski. It is shown that
this problem is caused by the singular nature of the on-shell expansion of the
fermion self-energy in the infra-red. Its regularization reveals that the
alleged gauge dependence pertains to the residue rather than the pole of the
fermion propagator, so that in particular the damping constant comes out
gauge-independent, as it should.Comment: 5 page
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