56 research outputs found
Pressure of the Standard Model at High Temperatures
We compute the pressure of the standard model at high temperatures in the
symmetric phase to three loops, or to O(g^5) in all coupling constants. We find
that the terms of the perturbative expansion in the SU(2) + Higgs sector
decrease monotonically with increasing order, but the large values of the
strong coupling constant g_s and the Yukawa coupling of the top quark g_Y make
the expansion in the full theory converge more slowly. The final result is
observed to be about 10% smaller than the ideal gas pressure commonly used in
cosmological calculations.Comment: 30 pages, 4 figures. v2: one reference added, minor revisions,
accepted for publication in JHE
Higher Order Corrections to the Equation of State of QED at High Temperature
We elaborate on the computation of the pressure of thermal quantum
electrodynamics, with massless electrons, to the fifth () order. The
calculation is performed within the Feynman gauge and the imaginary-time
formalism is employed. For the calculation, the method of Sudakov
decomposition is used to evaluate some ultraviolet finite integrals which have
a collinear singularity. For the contribution, we give an alternative
derivation and extend the discussion to massive electrons and nonzero chemical
potential. Comments are made on expected similarities and differences for
prospective three-loop calculations in QCD.Comment: (SPhT/94-086) (ANL-HEP-PR-94-32), 33 pages in latex, 5 figures
attached as postscript file
Thermal Effects in Low-Temperature QED
QED is studied at low temperature (, where is the electron mass)
and zero chemical potential. By integrating out the electron field and the
nonzero bosonic Matsubara modes, we construct an effective three-dimensional
field theory that is valid at distances . As applications, we
reproduce the ring-improved free energy and calculate the Debye mass to order
.Comment: 20 pages, 4 figures, revte
The pressure of QCD at finite temperatures and chemical potentials
The perturbative expansion of the pressure of hot QCD is computed here to
order g^6ln(g) in the presence of finite quark chemical potentials. In this
process all two- and three-loop one-particle irreducible vacuum diagrams of the
theory are evaluated at arbitrary T and mu, and these results are then used to
analytically verify the outcome of an old order g^4 calculation of Freedman and
McLerran for the zero-temperature pressure. The results for the pressure and
the different quark number susceptibilities at high T are compared with recent
lattice simulations showing excellent agreement especially for the chemical
potential dependent part of the pressure.Comment: 35 pages, 6 figures; text revised, one figure replace
Photon Propagation in Dense Media
Using thermal field theory, we derive simple analytic expressions for the
spectral density of photons in degenerate QED plasmas, without assuming the
usual non or ultra-relativistic limit. We recover the standard results in both
cases. Although very similar in ultra-relativistic plasmas, transverse and
longitudinal excitations behave very differently as the electron Fermi momentum
decreases.Comment: 12pp (3 PS figures available upon request), ENSLAPP-A-412/9
Next-to-leading Order Debye Mass for the Quark-gluon Plasma
The Debye screening mass for a quark-gluon plasma at high temperature is
calculated to next-to-leading order in the QCD coupling constant from the
correlator of two Polyakov loops. The result agrees with the screening mass
defined by the location of the pole in the gluon propagator as calculated by
Rebhan. It is logarithmically sensitive to nonperturbative effects associated
with the screening of static chromomagnetic fields.Comment: 8 pages, NUHEP-TH-94-1
Quark number susceptibilities of hot QCD up to g^6ln(g)
The pressure of hot QCD has recently been determined to the last
perturbatively computable order g^6 ln(g) by Kajantie et al. using
three-dimensional effective theories. A similar method is applied here to the
pressure in the presence of small but non-vanishing quark chemical potentials,
and the result is used to derive the quark number susceptibilities in the limit
mu = 0. The diagonal quark number susceptibility of QCD with n_f flavours of
massless quarks is evaluated to order g^6ln(g) and compared with recent lattice
simulations. It is observed that the results qualitatively resemble the lattice
ones, and that when combined with the fully perturbative but yet undetermined
g^6 term they may well explain the behaviour of the lattice data for a wide
range of temperatures.Comment: 11 pages, 3 figures Typos corrected, references added, figures
modifie
The Three Loop Equation of State of QED at High Temperature
We present the three loop contribution (order ) to the pressure of
massless quantum electrodynamics at nonzero temperature. The calculation is
performed within the imaginary time formalism. Dimensional regularization is
used to handle the usual, intermediate stage, ultraviolet and infrared
singularities, and also to prevent overcounting of diagrams during resummation.Comment: ANL-HEP-PR-94-02, SPhT/94-054 (revised final version
Damping rates for moving particles in hot QCD
Using a program of perturbative resummation I compute the damping rates for
fields at nonzero spatial momentum to leading order in weak coupling in hot
. Sum rules for spectral densities are used to simplify the calculations.
For massless fields the damping rate has an apparent logarithmic divergence in
the infrared limit, which is cut off by the screening of static magnetic fields
(``magnetic mass''). This demonstrates how at high temperature even
perturbative quantities are sensitive to nonperturbative phenomenon.Comment: LaTeX file, 24 pages, BNL-P-1/92 (December, 1992
Periodic ground state for the charged massive Schwinger model
It is shown that the charged massive Schwinger model supports a periodic
vacuum structure for arbitrary charge density, similar to the common
crystalline layout known in solid state physics. The dynamical origin of the
inhomogeneity is identified in the framework of the bozonized model and in
terms of the original fermionic variables.Comment: 19 pages, 10 figures, revised version, accepted in Phys. Rev.
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