Non-standard primordial fluctuations and nongaussianity in string
  inflation
  Inflationary scenarios in string theory often involve a large number of light
scalar fields, whose presence can enrich the post-inflationary evolution of
primordial fluctuations generated during the inflationary epoch. We provide a
simple example of such post-inflationary processing within an explicit
string-inflationary construction, using a Kahler modulus as the inflaton within
the framework of LARGE Volume Type-IIB string flux compactifications. We argue
that inflationary models within this broad category often have a selection of
scalars that are light enough to be cosmologically relevant, whose
contributions to the primordial fluctuation spectrum can compete with those
generated in the standard way by the inflaton. These models consequently often
predict nongaussianity at a level, f_NL ~ O(10), potentially observable by the
Planck satellite, with a bi-spectrum maximized by triangles with squeezed shape
in a string realisation of the curvaton scenario. We argue that the observation
of such a signal would robustly prefer string cosmologies such as these that
predict a multi-field dynamics during the very early universe.
