NON-GAUSSIAN ISOCURVATURE PERTURBATIONS FROM GOLDSTONE MODES GENERATED DURING INFLATION

We investigate non-Gaussian isocurvature perturbations generated by th e evolution of Goldstone modes during inflation. If a global symmetry is broken before inflation, the resulting Goldstone modes are disorder ed during inflation in a precise and predictable way. After inflation these Goldstone modes order themselves in a self-similar way, much as Goldstone modes in field ordering scenarios based on the Kibble mechan ism. For (H-inf(2)/M-Pl(2))similar to 10(-6), through their gravitatio nal interaction these Goldstone modes generate density perturbations o f approximately the right magnitude to explain the cosmic microwave ba ckground (CMB) anisotropy and seed the structure seen in the universe today.; We point out that for the pattern of symmetry breaking in whic h a global U(1) is completely broken, the inflationary evolution of th e Goldstone field may be treated as that of a massless scalar field. U nlike the more commonly discussed case in which a global U(1) is compl etely broken in a cosmological phase transition, in the inflationary c ase the production of defects can be made exponentially small. so that Goldstone field evolution is completely linear. In such a model non-G aussian perturbations result because tb lowest order density perturbat ions are sourced by products of Gaussian fields. Consequently, in this non-Gaussian model N-point correlations may be calculated by evaluati ng Feynman diagrams. We explore the issue of phase dispersion and conc lude that this non-Gaussian model predicts Doppler peaks in the CMB an isotropy.