Local non-Gaussianity from inflation

Understand

The non-Gaussian distribution of primordial perturbations has the potential to reveal the physical processes at work in the very early Universe.

• Local models provide a well-defined class of non-Gaussian distributions that arise naturally from the non-linear evolution of density perturbations on super-Hubble scales starting from Gaussian field fluctuations during inflation.
• I describe the delta-N formalism used to calculate the primordial density perturbation on large scales and then review several models for the origin of local primordial non-Gaussianity, including the cuvaton, modulated reheating and ekpyrotic scenarios.
• I include an appendix with a table of sign conventions used in specific papers.