Study of the Inflationary Spectrum in the Presence of Quantum Gravity Corrections

Abstract

After a brief review of the different approaches to predicting the possible quantum gravity corrections to quantum field theory, we discuss in some detail the formulation based on a Gaussian reference frame fixing. Then, we utilize this scenario in the determination of the inflationary spectrum of primordial perturbations. We consider the quantization of an inhomogeneous, free, massless scalar field in a quasi-classical isotropic Universe by developing a WKB expansion of the dynamics of the next order in the Planckian parameter, with respect to the one at which standard QFT emerges. The quantum gravity corrections to the scale-invariant spectrum are discussed in a specific primordial cosmological setting and then in a general minisuperspace formalism, showing that there is no mode-dependent effect, and thus the scale invariant inflationary spectrum is preserved. This result is discussed in connection to the absence of a matter backreaction on the gravitational background in the considered paradigm.