SÉMINAIRE DU GRECO
"A Statistical approach to multifield inflation: manyfield perturbations beyond slow roll" 

SÃ©bastien RenauxPetel 

We study multifield contributions to the scalar power spectrum in an ensemble of sixfield inflationary models obtained in string theory. We identify examples in which inflation occurs by chance, near an approximate inflection point, and we compute the primordial perturbations numerically, both exactly and using an array of truncated models. The scalar mass spectrum and the number of fluctuating fields are accurately described by a simple random matrix model. During the approach to the inflection point, bending trajectories and violations of slow roll are commonplace, and 'manyfield' effects, in which three or more fields influence the perturbations, are often important. However, in a large fraction of models consistent with constraints on the tilt, the signatures of multifield evolution occur on unobservably large scales. Our scenario is a concrete microphysical realization of quasisinglefield inflation, with scalar masses of order the Hubble parameter, but the cubic and quartic couplings are typically too small to produce detectable nonGaussianity. We argue that our results are characteristic of a broader class of models arising from multifield potentials that are natural in the Wilsonian sense.


lundi 13 mai 201³  1q:02 Salle des sÃ©minaires FranÃ§ois Arago, Institut d'Astrophysique de Paris 
