Particle production, back reaction and singularity avoidance

We consider particle production in Robertson-Walker spacetime as particle-a ntiparticle rotation. We thereby obtain a scale factor that guarantees part icle production. We then study quantum field effects in spatially flat homo geneous and isotropic spacetime with energy density of created particles an d one loop quantum correction as back reaction. In the numerical solution i nitial values are determined from particle production simulated scale facto r and obtain the evolution of the universe both at early and late times hav ing a bounce.