Origin of inflation in CFT driven cosmology: R^2gravity and nonminimally coupled inflaton models
Abstract
We present a detailed derivation of the recently suggested new type of hilltop inflation [arXiv:1509.07270] originating from the microcanonical density matrix initial conditions in cosmology driven by conformal field theory (CFT). The cosmological instantons of topology S^1× S^3, which set up these initial conditions, have the shape of a garland with multiple periodic oscillations of the scale factor of the spatial S^3section. They describe underbarrier oscillations of the inflaton and scale factor in the vicinity of the inflaton potential maximum, which gives a sufficient amount of inflation required by the known CMB data. We build the approximation of two coupled harmonic oscillators for these garland instantons and show that they can generate inflation consistent with the parameters of the CMB primordial power spectrum in the nonminimal Higgs inflation model and in R^2 gravity. In particular, the instanton solutions provide smallness of inflationary slowroll parameters ɛ and η <0 and their relation ɛ ∼ η ^2 characteristic of these two models. We present the mechanism of formation of hilllike inflaton potentials, which is based on logarithmic loop corrections to the asymptotically shiftinvariant treelevel potentials of these models in the Einstein frame. We also discuss the role of R^2gravity as an indispensable finite renormalization tool in the CFT driven cosmology, which guarantees the nondynamical (ghost free) nature of its scale factor and special properties of its cosmological garlandtype instantons. Finally, as a solution to the problem of hierarchy between the Planckian scale and the inflation scale we discuss the concept of a hidden sector of conformal higher spin fields.
 Publication:

European Physical Journal C
 Pub Date:
 December 2015
 DOI:
 10.1140/epjc/s1005201538177
 arXiv:
 arXiv:1510.06858
 Bibcode:
 2015EPJC...75..584B
 Keywords:

 Conformal field theory;
 Quantum cosmology;
 Inflation;
 High Energy Physics  Theory;
 General Relativity and Quantum Cosmology
 EPrint:
 final version, to be published in European Physical Journal C. arXiv admin note: text overlap with arXiv:1509.07270