Slowly decaying classical fields, unitarity, and gauge invariance

Abstract

In classical external gauge fields that fall off less fast than the inverse of the evolution parameter (time) of the system the implementability of a unitary perturbative scattering operator ($S$-matrix) is not guaranteed, although the field goes to zero. The importance of this point is exposed for the counter-example of low-dimensionally expanding systems. The issues of gauge invariance and of the interpretation of the evolution at intermediate times are also intricately linked to that point.

8 pages, no figures

References in corpus (3)

• Soft-Gluon Production Due to a Gluon Loop in a Constant Chromo-Electric Background Field
• Quark-antiquark pair production in space-time dependent fields
• Gluon propagation in space-time dependent fields

Cited by in corpus (3)

• Transverse and longitudinal momentum spectra of fermions produced in strong SU(2) fields
• Concerning gauge field fluctuations around classical configurations
• On invariants for particle propagation in non-Abelian fields