Axions, neutrinos and strings: The formation of structure in an SO(10) universe

The author reports on work with Qaisar Shafi where they consider a class of grand unified theories in which cosmologically significant axion and neutrino energy densities arise naturally. To obtain large scale structure they consider (1) an inflationary scenario, (2) inflation followed by string production, and (3) a non-inflationary scenario with density fluctuations caused solely by strings. They show that inflation may be compatible with the recent observational indications that Ω < 1 on the scale of superclusters, particularly if strings are present