arXiv subjects
Publications and source records attributed to Christof Wetterich.
We present an exact nonperturbative flow equation for the average action for quarks which incorporates the effects of gluon fluctuations. With suitable truncations this allows one to compute effective multiquark interactions in dependence on an infrared scale $k$. Our method amounts to integrating out the gluons with momenta larger than $k$.
A systematic loop expansion is formulated in terms of full propagators and vertices. It is based on an expansion of the general solution of an exact non-perturbative flow equation.
We discuss the electroweak phase-transition in the early universe, using non-perturbative flow equations for a computation of the free energy. For a scalar mass above $\sim 70$ GeV, high-temperature perturbation theory cannot describe this transition reliably. This is due to the dominance of three-dimensional physics at high temperatures which implies that the effective gauge coupling grows strong in the symmetric phase. We give an order of magnitude-estimate of nonperturbative effects in reasonable agreement with recent results from electroweak lattice simulations. (Talk given by C. Wetterich at the 3rd Colloque Cosmologie, Paris, June 7-9, 1995, to appear in the proceedings)
For realistic values of the Higgs boson mass the high temperature electroweak phase transition cannot be described perturbatively. The symmetric phase is governed by a strongly interacting $SU(2)$ gauge theory. Typical masses of excitations and scales of condensates are set by the ``high temperature confinement scale'' $\approx 0.2\ T$. For a Higgs boson mass around 100 GeV or above all aspects of the phase transition are highly nonperturbative. Near the critical temperature strong electroweak interactions are a dominant feature also in the phase with spontaneous symmetry breaking. Depending on the value of the Higgs boson mass the transition may be a first order phase transition or an analytical crossover.