Fully radiative electroweak symmetry breaking

Abstract

Models of Gauge-Higgs unification in extra dimensions offer a very elegant playground where one can study electroweak symmetry breaking. The Higgs potential is fully radiatively generated and the contribution of bulk fermions will induce a vacuum expectation value. A generic problem is that the quartic scalar coupling is too low, resulting in a Higgs VEV that is too close to the compactification scale, and a Higgs mass that is too light. In this paper we show that it is possible to solve these problems in a minimal scenario in flat space by cancellations in the Higgs potential between the contribution of different bulk fermions. A crucial role is played by antiperiodic fermions: the cancellation is not the result of a fine tuning, but rather dictated by the choice of representations and parities of the fermions. We also show that introducing a relatively large representation can help in achieving a sufficiently heavy top. In this case, the strong coupling scale is lowered to a marginally acceptable value, and a more careful analysis of two loop effects should decide if the theory remains under perturbative control. © SISSA 2006.