Fluctuations in the inflationary universe

In the usual treatment of the inflationary universe, it is assumed that the expectation value of some component of the Higgs field develops a non-zero symmetry breaking value PHI0. However, in the models normally considered, the expectation value of PHI will be zero at all times because PHI and -PHI are equally probable. To overcome this difficulty, we calculate the effective action as a function of < PHI2> rather than . This also solves the infra-red problem associated with a Coleman-Weinberg condition in de Sitter space. The expectation value of PHI2 grows linearly with time at first and then as (t2 - t)-1. The irregularities in the resulting universe are smaller than those predicted by previous authors, though in the case of the standard SU(5) GUT they are still bigger than the limit set by the microwave background. (orig.)