14 research outputs found
Angular intricacies in hot gauge field theories
It is argued that in hot gauge field theories, "Hard Thermal Loops" leading
order calculations call for a definite sequence of angular averages and
discontinuity (or Imaginary part prescription) operations, and run otherwise
into incorrect results. The ten years old collinear singularity problem of hot
, provides a striking illustration of that fate.Comment: 14 pages, 1 figur
Two-loop Compton and annihilation processes in thermal QCD
We calculate the Compton and annihilation production of a soft static lepton
pair in a quark-gluon plasma in the two-loop approximation. We work in the
context of the effective perturbative expansion based on the resummation of
hard thermal loops. Double counting is avoided by subtracting appropriate
counterterms. It is found that the two-loop diagrams give contributions of the
same order as the one-loop diagram. Furthermore, these contributions are
necessary to obtain agreement with the naive perturbative expansion in the
limit of vanishing thermal masses.Comment: Latex, 24 pages, postscript figures included with the package
graphic
Proof of a mass singularity free property in high temperature QCD
It is shown that three series of diagrams entering the calculation of some
hot process, are mass (or collinear) singularity free, indeed. This
generalizes a result which was recently established up to the third non trivial
order of (thermal) Perturbation Theory.Comment: 40 pages, 3 figures. to be published in J. Math. Phys. no. 44, 200
Real time thermal propagtors for massive gauge bosons
We derive Feynman rules for gauge theories exhibiting spontaneous symmetry
breaking using the real-time formalism of finite temperature field theory. We
also derive the thermal propagators where only the physical degrees of freedom
are given thermal boundary conditions. We analyse the abelian Higgs model and
find that these new propagators simplify the calculation of the thermal
contribution to the self energy.Comment: 7 pages, late
Non-Fermi-liquid effect in magnetic susceptibility
Taking into account the anomalous self-energy for quarks due to the dynamic
screening effect for the transverse gluon propagator, we study the temperature
dependence of the magnetic susceptibility in detail. It is shown that there
does not exist the term in the susceptibility, different from the
specific heat, but an anomalous term arises instead as a novel
non-Fermi-liquid effect.Comment: 10 pages, 1 figur
Finite temperature amplitudes and reaction rates in Thermofield dynamics
We propose a method for calculating the reaction rates and transition
amplitudes of generic process taking place in a many body system in
equilibrium. The relationship of the scattering and decay amplitudes as
calculated in Thermo Field Dynamics the conventional techniques is established.
It is shown that in many cases the calculations are relatively easy in TFD.Comment: 32 pages, RevTex, 2 PS figures, to appear in Phys. Rev.
Two problems in thermal field theory
In this talk, I review recent progress made in two areas of thermal field
theory. In particular, I discuss various approaches for the calculation of the
quark gluon plasma thermodynamical properties, and the problem of its photon
production rate.Comment: 10 pages Latex document, 15 postscript figures. Invited talk given at
the 6th Workshop on High Energy Particle Physics, Chennai, India, 3-15 Jan
200
Spontaneous magnetization in QCD and non-Fermi-liquid effects
Magnetic properties of quark matter at finite temperature are discussed by
evaluating the magnetic susceptibility. Combining the microscopic calculation
of the self-energy for quarks as well as the screening effects for gluons with
Fermi-liquid theory in a consistent way, we study the temperature dependence of
the magnetic susceptibility. The longitudinal gluons have the static screening
given by the Debye mass, and have a standard temperature dependence of
. An anomalous term arises in the magnetic susceptibility as
a novel non-Fermi-liquid effect due to the anomalous self-energy for quarks
given by the dynamic screening for transverse gluons. We then extract the
critical(Curie) temperature and present the magnetic phase diagram on the
density-temperature plane.Comment: 14 pages, 6 figures; Secs. 1 and 5 have been revise