Informal Pizza Seminars

Nongaussian Fluctuations from IR Cascading During Inflation

Neil Barnaby

University of Toronto

I will discuss a new mechanism for generating cosmological fluctuations from infra-red (IR) cascading during inflation. The prototype example of this scenario is a simple model with inflaton and iso-inflaton fields coupled in such a way that the latter becomes massless momentarily during inflation. Iso-inflaton particles are produced at this instant, slowing down the motion of the background. Very quickly the produced iso-inflaton particles become non-relativistic and their multiple rescatterings off the condensate leads to bremschtrahlung radiation of light inflaton IR fluctuations. This process of IR cascading leads to a variety of novel observational signatures, including features in the power spectrum and large nongaussianities with a unique shape dependence. I will discuss the observational constraints on particle production during inflation and also possible realizations of this scenario in string theory.