We study how inflationary observables associated with primordial tensor modes are affected by coupling the minimal field content with an extra spin-2 particle during inflation. We work with a model that is ghost-free at the fully non-linear level and show how the new degrees of freedom modify standard consistency relations for the tensor bispectrum. The extra interacting spin-2 field is necessarily massive and unitarity dictates its mass be in the m∼ H range. Despite the fact that this bound selects a decaying solution for the corresponding tensor mode, cosmological correlators still carry the imprints of such fossil fields. Indeed, fossil(s) can in general lead to anisotropies in observables such as the tensor power spectrum. We show how this plays out in our set-up.
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Dimastrogiovanni, E. (Creator), Fasiello, M. R. (Creator) & Tasinato, G. (Creator), IOP Publishing, 13 Aug 2018