Gluon propagation in space-time dependent fields

The propagator for gluons in a space-time dependent field is derived. This is accomplished by solving the equation of motion for the gluonic Green's functions. Subsequently a relationship between the quark and the gluon propagator is presented. With its help characteristics of the bosonic propagator can be obtained from those of the fermionic and vice versa. Finally, this relation is discussed for the special case of ultrarelativistic collisions in the semiclassical limit.Comment: 14 pages, no figures, typos correcte

Fermion production in classical fields

The creation of quark-antiquark pairs by vacuum polarisation in the presence of classical fields is studied based on their propagators in the background. Especially the issue of gauge invariance and particularities of particle production in ultrarelativistic collider experiments are discussed.Comment: To appear in the proceedings of the 6th Conference on Strong and Electroweak Matter 2004 (SEWM04), Helsinki, Finland, 16-19 Jun 2004. 5 pages, no figure

Equilibration of right-handed electrons

We study the equilibration of right-handed electrons in the symmetric phase of the Standard Model. Due to the smallness of the electron Yukawa coupling, it happens relatively late in the history of the Universe. We compute the equilibration rate at leading order in the Standard Model couplings, by including gauge interactions, the top Yukawa- and the Higgs self-interaction. The dominant contribution is due to $2 \to 2$ particle scattering, even though the rate of (inverse) Higgs decays is strongly enhanced by multiple soft scattering which is included by Landau-Pomeranchuk-Migdal (LPM) resummation. Our numerical result is substantially larger than approximations presented in previous literature.Comment: 31 pages, 5 figures. v2: Added appendix estimating the conversion of right-handed electron number into hypermagnetic fields through the chiral anomaly. References added, minor errors corrected, results and conclusions unchanged, published versio

Walking in the SU(N)

We study the phase diagram as function of the number of colours and flavours of asymptotically free non-supersymmetric theories with matter in higher dimensional representations of arbitrary SU(N) gauge groups. Since matter in higher dimensional representations screens more than in the fundamental a general feature is that a lower number of flavours is needed to achieve a near-conformal theory. We study the spectrum of the theories near the fixed point and consider possible applications of our analysis to the dynamical breaking of the electroweak symmetry.Comment: 12 page