SELF-CONSISTENT SOLUTION TO THE BACK-REACTION PROBLEM FOR VECTOR-FIELDS IN 2 DIMENSIONS

We describe vector fields propagating in a two-dimensional spatially flat Robertson-Walker background using a curved space-time generalization of the Stueckelberg formalism. We prove that the energy-momentum tensor expectation value in the vacuum defined through energy minimization is renormalizable and yields the usual anomalous trace in the massless limit of vector mesons. Further on we study the back-reaction problem using the semiclassical Einstein equations. In the massive case we found that the physical solution requires the cosmological constant to vanish but not necessarily with a vanishing curvature. However, for certain initial conditions of the scale factor, the de Sitter metric is a consistent solution with the cosmological constant depending on powers of the curvature scalar greater than one. In addition, matter is continuously being created at a steady state.