Journal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
Volume -, Issue 9, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2017/09/043
Keywords
inflation; primordial gravitational waves (theory); non-gaussianity; modified gravity
Funding
- grant Theoretical Astroparticle Physics under the program PRIN - MIUR [2012CPPYP7]
- TASP (iniziativa specifica INFN)
- Programme National de Cosmologie and Galaxies (PNCG) of CNRS/INSU, France
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We study generalized disformal transformations, including derivatives of the metric, in the context of the Effective Field Theory of Inflation. All these transformations do not change the late-time cosmological observables but change the coefficients of the operators in the action: some couplings are effectively redundant. At leading order in derivatives and up to cubic order in perturbations, one has 6 free functions that can be used to set to zero 6 of the 17 operators at this order. This is used to show that the tensor three-point function cannot be modified at leading order in derivatives, while the scalar-tensor-tensor correlator can only be modified by changing the scalar dynamics. At higher order in derivatives there are transformations that do not affect the Einstein-Hilbert action: one can find 6 additional transformations that can be used to simplify the inflaton action, at least when the dynamics is dominated by the lowest derivative terms. We also identify the leading higher-derivative corrections to the tensor power spectrum and bispectrum.
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