F. T. Brandt

General structure of the photon self-energy in noncommutative QED

We study the behavior of the photon two point function, in noncommutative QED, in a general covariant gauge and in arbitrary space-time dimensions. We show, to all orders, that the photon self-energy is transverse. Using an appropriate extension of the dimensional regularization method, we evaluate the one-loop corrections, which show that the theory is renormalizable. We also prove, to all orders, that the poles of the photon propagator are gauge independent and briefly discuss some other related aspects.

High-temperature QCD and the classical Boltzmann equation in curved spacetime

Abstract 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 [P.F. Kelly et al., Phys. Rev. D 50 (1994) 4209]. 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.

Metric dependence of partition function at high temperature

Abstract This paper is about thermal field theory in a background gravitational field (in space-time which is asymptotically minkowskian). We use the analytically continued imaginary-time formalism in one-loop order, and restrict ourselves to high temperatures. An all-orders, but implicit, expression is given for the partition function.

General covariant gauge fixing for massless spin-two fields

The most general covariant gauge fixing Lagrangian is considered for a spin-two gauge theory in the context of the Faddeev-Popov procedure. In general, five parameters characterize this gauge fixing. Certain limiting values for these parameters give rise to a spin-two propagator that is either traceless or transverse, but for no values of these parameters is this propagator simultaneously traceless and transverse. Having a traceless-transverse propagator ensures that only the physical degrees of freedom associated with the tensor field propagate, and hence it is analogous to the Landau gauge in electrodynamics. To obtain such a traceless-transverse propagator, a gauge fixing Lagrangian which is not quadratic must be employed; this sort of gauge fixing Lagrangian is not encountered in the usual Faddeev-Popov procedure. It is shown that when this nonquadratic gauge fixing Lagrangian is used, two fermionic and one bosonic ghosts arise. As a simple application we discuss the energy-momentum tensor of the gravitational field at finite temperature.

Three-graviton vertex function in thermal quantum gravity.

The high-temperature limit of the three-graviton vertex function is studied in thermal quantum gravity, to one-loop order. The leading (

Structure of the graviton self-energy at finite temperature

{T}^{4}

The energy of the high-temperature quark-gluon plasma

) contributions arising from internal gravitons are calculated and shown to be twice the ones associated with internal scalar particles, in correspondence with the two helicity states of the graviton. The gauge invariance of this result follows as a consequence of the Ward and Weyl identities obeyed by the thermal loops, which are verified explicitly.

The long wavelength limit of hard thermal loop effective actions

We study the graviton self-energy function in a general gauge, using a hard thermal loop expansion which includes terms proportional to

The Static effective action for noncommutative QED at high temperature

{T}^{4},