Primordial Perturbations from Multifield Inflation with Nonminimal Couplings

Understand

Realistic models of particle physics include many scalar fields.

• These fields generically have nonminimal couplings to the Ricci curvature scalar, either as part of a generalized Einstein theory or as necessary counterterms for renormalization in curved background spacetimes.
• We develop a gauge-invariant formalism for calculating primordial perturbations in models with multiple nonminimally coupled fields.
• We work in the Jordan frame (in which the nonminimal couplings remain explicit) and identify two distinct sources of entropy perturbations for such models.