A graceful end to inflation

Guth has suggested that if the Universe underwent extreme supercooling during the phase transition associated with the spontaneous symmetry breaking (SSB) of the Grand Unified Theory (GUT), then a number of apparent 'cosmological puzzles' could be explained (the so-called 'inflationary Universe'). Among these puzzles are the isotropy, homogeneity, flatness/oldness, and monopole problems. The scenario in its original form while very attractive, suffered from the apparent lack of a 'graceful return' from the inflationary phase to a hot, Friedmann-Robertson-Walker cosmology. Recently, a new inflationary scenario has been suggested which appears to solve the 'graceful return' problem while retaining the other desirable features. I shall discuss the detailed evolution of the Higgs field responsible for SSB, and the temperature and scale factor of the Universe in this new scenario. Numerical calculations show that sufficient inflation can occur to solve the 'cosmological conundrums', and that the Universe smoothly reheats to a temperature of 0(1014 GeV), insuring that baryogenesis can proceed in the usual way. I will also give a very optimistic appraisal of 'the present minimal SU(5) model'. It now appears that we have an affective, low-energy ( < approximately 1015GeV) theory which accounts for our present understanding of particle physics, which has many beneficial consequences for cosmology, and which at present, does not suffer from any known 'fatal disease'