M. E. Carrington

The 4PI effective action for \(\phi^4\) theory

Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000. The corresponding integrated luminosity is 650 pb^{-1}. The values of the cross-section obtained are found to be in agreement with QED predictions. Limits on the anomalous magnetic and electric dipole moments of the tau lepton are deduced.

Fermion mass at next-to-leading order in the hard thermal loop effective theory

The calculation of the real part of a quasiparticle dispersion relation at next-to-leading order in the hard thermal loop effective theory is a very difficult problem. Even though the hard thermal loop effective theory is almost 20 years old, there is only one next-to-leading order calculation of the real part of a quasiparticle dispersion relation in the literature [H. Schulz, Nucl. Phys. B413, 353 (1994)]. In this paper, we calculate the fermion mass in QED and QCD at next-to-leading order. For QED the result is

QED electrical conductivity using the two-particle-irreducible effective action

M=eT/\sqrt{8}(1\ensuremath{-}(1.427\ifmmode\pm\else\textpm\fi{}0.02)e/4\ensuremath{\pi})

Shear viscosity in phi**4 theory from an extended ladder resummation

and for QCD with

Perturbative and non-perturbative Kolmogorov turbulence in a gluon plasma

{N}_{f}=2

Renormalization group methods and the 2PI effective action

and

Energetic dileptons from the quark-gluon plasma

{N}_{c}=3

Cancellation of ladder graphs in an effective expansion

we obtain

Towards next-to-leading order transport coefficients from the four-particle irreducible effective action

M=gT/\sqrt{6}(1+(1.867\ifmmode\pm\else\textpm\fi{}0.02)g/4\ensuremath{\pi})

Leading order QCD shear viscosity from the three-particle irreducible effective action

.