65 research outputs found
Thermal one- and two-graviton Green's functions in the temporal gauge
The thermal one- and two-graviton Green's function are computed using a
temporal gauge. In order to handle the extra poles which are present in the
propagator, we employ an ambiguity-free technique in the imaginary-time
formalism. For temperatures T high compared with the external momentum, we
obtain the leading T^4 as well as the subleading T^2 and log(T) contributions
to the graviton self-energy. The gauge fixing independence of the leading T^4
terms as well as the Ward identity relating the self-energy with the one-point
function are explicitly verified. We also verify the 't Hooft identities for
the subleading T^2 terms and show that the logarithmic part has the same
structure as the residue of the ultraviolet pole of the zero temperature
graviton self-energy. We explicitly compute the extra terms generated by the
prescription poles and verify that they do not change the behavior of the
leading and sub-leading contributions from the hard thermal loop region. We
discuss the modification of the solutions of the dispersion relations in the
graviton plasma induced by the subleading T^2 contributions.Comment: 17 pages, 5 figures. Revised version to be published in Phys. Rev.
Classical transport equation in non-commutative QED at high temperature
We show that the high temperature behavior of non-commutative QED may be
simply obtained from Boltzmann transport equations for classical particles. The
transport equation for the charge neutral particle is shown to be
characteristically different from that for the charged particle. These
equations correctly generate, for arbitrary values of the non-commutative
parameter theta, the leading, gauge independent hard thermal loops, arising
from the fermion and the gauge sectors. We briefly discuss the generating
functional of hard thermal amplitudes.Comment: 11 page
Vanishing magnetic mass in QED with a Chern-Simons term
We show that, at one loop, the magnetic mass vanishes at finite temperature
in QED in any dimension. In QED, even the zero temperature part can be
regularized to zero. We calculate the two loop contributions to the magnetic
mass in QED with a Chern-Simons term and show that it vanishes. We give a
simple proof which shows that the magnetic mass vanishes to all orders at
finite temperature in this theory. This proof also holds for QED in any
dimension.Comment: revtex, 7 pages, 5 figure
On the Free Energy of Noncommutative Quantum Electrodynamics at High Temperature
We compute higher order contributions to the free energy of noncommutative
quantum electrodynamics at a nonzero temperature . Our calculation includes
up to three-loop contributions (fourth order in the coupling constant ). In
the high temperature limit we sum all the {\it ring diagrams} and obtain a
result which has a peculiar dependence on the coupling constant. For large
values of ( is the magnitude of the noncommutative
parameters) this non-perturbative contribution exhibits a non-analytic behavior
proportional to . We show that above a certain critical temperature, there
occurs a thermodynamic instability which may indicate a phase transition.Comment: 28 pages, 37 figures. Matches published version in Nuclear Physics
High-temperature QCD and the classical Boltzmann equation in curved spacetime
It has been shown that the high-temperature limit of perturbative thermal QCD
is easily obtained from the Boltzmann transport equation for `classical'
coloured particles. We generalize this treatment to curved space-time. We are
thus able to construct the effective stress-energy tensor. We give a
construction for an effective action. As an example of the convenience of the
Boltzmann method, we derive the high-temperature 3-graviton function. We
discuss the static case.Comment: uuencoded gz-compressed .dvi fil
Scattering amplitudes at finite temperature
We present a simple set of rules for obtaining the imaginary part of a self
energy diagram at finite temperature in terms of diagrams that correspond to
physical scattering amplitudes.Comment: 23 pages in Revtex, with 33 eps-figure
Fermionic Contributions to the Free Energy of Noncommutative Quantum Electrodynamics at High Temperature
We consider the fermionic contributions to the free energy of noncommutative
QED at finite temperature . This analysis extends the main results of our
previous investigation where we have considered the pure bosonic sector of the
theory. For large values of ( is the magnitude of the
noncommutative parameters) the fermionic contributions decrease the value of
the critical temperature, above which there occurs a thermodynamic instability.Comment: 6 pages, 3 figures. To be published in Physics Letters
The energy of the high-temperature quark-gluon plasma
For the quark-gluon plasma, an energy-momentum tensor is found corresponding
to the high-temperature Braaten-Pisarski effective action. The tensor is found
by considering the interaction of the plasma with a weak gravitational field
and the positivity of the energy is studied. In addition, the complete
effective action in curved spacetime is written down.Comment: 13 pages, one figure, plain TeX forma
Transport equation for the photon Wigner operator in non-commutative QED
We derive an exact quantum equation of motion for the photon Wigner operator
in non-commutative QED, which is gauge covariant. In the classical
approximation, this reduces to a simple transport equation which describes the
hard thermal effects in this theory. As an example of the effectiveness of this
method we show that, to leading order, this equation generates in a direct way
the Green amplitudes calculated perturbatively in quantum field theory at high
temperature.Comment: 13 pages, twocolumn revtex4 styl
Non-commutative Oscillators and the commutative limit
It is shown in first order perturbation theory that anharmonic oscillators in
non-commutative space behave smoothly in the commutative limit just as harmonic
oscillators do. The non-commutativity provides a method for converting a
problem in degenerate perturbation theory to a non-degenerate problem.Comment: Latex, 6 pages, Minor changes and references adde
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