CONSTRAINTS ON INFLATIONARY SOLUTIONS IN THE PRESENCE OF SHEAR AND BULK VISCOSITY

Inflationary models and their claim to solve many of the outstanding p roblems in cosmology have been the subject of a great deal of debate o ver the last few years, A major sticking point has been the lack of bo th good observational and theoretical arguments to single out one part icular model out of the many that solve these problems. Here we examin e the degree of restrictiveness on the dynamical relationship between the cosmological scale factor and the inflation driving self-interacti on potential of a minimally coupled scalar field, imposed by the condi tion that the scalar field is required to be real during a classical r egime (the reality condition). We systematically look at the effects o f this constraint on many of the inflationary models found in the lite rature within the FLRW framework, and also look at what happens when p hysically motivated perturbations such as shear and bulk viscosity are introduced. We find that in many cases, either the models are totally excluded or the reality condition gives rise to constraints on the sc ale factor and on the various parameters of the model.