A NEW METHOD OF GENERATING EXACT INFLATIONARY SOLUTIONS

The mechanism of the initial inflation of the universe is based on gra vitationally coupled scalar fields phi. Various scenarios are distingu ished by the choice of an effective self-interaction potential U(phi) which simulates a temporarily nonvanishing cosmological term. Using th e Hubble expansion parameter H as a new ''time'' coordinate, we can fo rmally derive the general Robertson-Walker metric for a spatially flat cosmos. Our new method provides a classification of allowed inflation ary potentials and is broad enough to embody all known exact solutions involving one scalar field as special cases. Moreover, we present new inflationary and deflationary exact solutions and can easily predict the influence of the form of U(phi) on density perturbations.