Non-standard primordial fluctuations and nongaussianity in string inflation

Understand

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.