Gauge theories in external electromagnetic fields: The standard SU(2)xU(1) model

Spontaneously broken SU(2)xU(1) electroweak theory in a constant background electromagnetic field is shown to admit a phase transition to a restored symmetry phase for large values of the external field. Allowing for two arbitrary parameters, the Higgs mass and the expectation value of the Higgs field, we derive a lower bound on the critical magnetic field required for restoration. The configuration space heat kernel method adapted to dimensional regularization techniques is used allowing calculations to be performed in arbitrary renormalizable gauges. (author)