GEOMETRIC GAUGE-FIELDS, PARTICLE-PRODUCTION, AND TIME

The geometric magnetic- and electric-type fields are shown to have nontrivial effects in the form of semiclassical back reactions from quantized matter fields on the adiabatically evolving classical background geometry. As a consequence of the gauge invariance of the induced reaction forces it then follows that the matter vacuum polarization in a space-time emerging out from a flat simply connected superspace does not have a gravitational effect. However, the vacuum instability and the associated particle production do have a nonzero back reaction which gets encoded in the electric scalar potential. The relationship between the standard semiclassical definition of time and the existence of a nontrivial Berry phase is also explored. This offers an interesting constraint on the initial quantum state of the Universe.