Khronon inflation

摘要

We study the possibility that the approximate time shift symmetry duringinflation is promoted to the full invariance under time reparametrization t \to\tilde t(t), or equivalently under field redefinition of the inflaton \phi \to\tilde\phi(\phi). The symmetry allows only two operators at leading order inderivatives, so that all n-point functions of scalar perturbations are fixed interms of the power spectrum normalization and the speed of sound. Duringinflation the decaying mode only decays as 1/a and this opens up thepossibility to violate some of the consistency relations in the squeezed limit,although this violation is suppressed by the (small) breaking of the fieldreparametrization symmetry. In particular one can get terms in the 3-pointfunction that are only suppressed by 1/k_L in the squeezed limit k_L \to 0compared to the local shape.