Subodh Patil (University of Geneva, Switzerland)
Although detecting primordial non-Gaussianity (NG) would provide an incredibly rich window onto the interaction physics of the inflaton, one might wonder what we could conclude about its nature if all we end up observing is consistent with adiabatic, Gaussian and scale invariant initial conditions. In this talk we highlight how in principle, one can still infer a great deal. Fields that are completely decoupled from the inflaton still interact with gravitational strength interactions, and although these interactions are very suppressed at low energies, a large number of them can consistently imprint interesting signatures on cosmological observables. If one were to assume nothing other than adiabaticity in the early universe, we discuss how one can use the absence of primordial NG to place bounds on the hidden field content of the universe. These bounds become more and more meaningful the more stringent the observational bounds become. We discuss the implications for various string theoretic and supersymmetric phenomenological scenarios and prospects from future observations.