Reflection symmetry breaking scenarios with minimal gauge form coupling in brane world cosmology

This article synthesises and extends recent work on the cosmological consequences of dropping the usual Z(2) reflection symmetry postulate in brane world scenarios. It is observed that for a cosmological model of homogeneous isotropic type, the relevant generalised Birkhoff theorem establishing staticity of the external vacuum in the maximally symmetric bulk outside a freely moving world brane will remain valid for the case of motion that is forced by minimal (generalised Wess-Zumino type) coupling to an external antisymmetric gauge field provided its kinetic action contribution has the usual homogeneous quadratic form. This means that the geometry on each side of the brane worldsheet will still be of the generalised Schwarzschild anti-de-Sitter type. The usual first integrated Friedmann equation for the Hubble expansion rate can thereby be straightforwardly generalised by inclusion of new terms involving 2 extra parameters, respectively, measuring the strength of the gauge coupling and the degree of deviation from reflection symmetry. Some conceivable phenomenological implications are briefly outlined, and corresponding limitations are derived for possible values of relevant parameters. (C) 2001 Elsevier Science B.V. All rights reserved.