New type of hill-top inflation

Journal of Cosmology and Astroparticle Physics Volume 2016, Issue 1, 20 January 2016, Article number 036 New type of hill-top inflation (Article) Barvinsky, A.O.abc , Kamenshchik, A.Yu.de , Nesterov, D.V.a a Theory Department, Lebedev Physics Institute, Leninsky Prospect 53, Moscow, Russian Federation b Department of Physics, Tomsk State University, Lenin Ave. 36, Tomsk, Russian Federation c Department of Physics and Astronomy, Pacific Institue for Theoretical Physics, University of British Columbia, 6224 Agricultural Road, Vancouver, BC, Canada View additional affiliations View references (61) Abstract We suggest a new type of hill-top inflation originating from the initial conditions in the form of the microcanonical density matrix for the cosmological model with a large number of quantum fields conformally coupled to gravity. Initial conditions for inflation are set up by cosmological instantons describing underbarrier oscillations in the vicinity of the inflaton potential maximum. These periodic oscillations of the inflaton field and cosmological scale factor are obtained within the approximation of two coupled oscillators subject to the slow roll regime in the Euclidean time. This regime is characterized by rapid oscillations of the scale factor on the background of a slowly varying inflaton, which guarantees smallness of slow roll parameters and η of the following inflation stage. A hill-like shape of the inflaton potential is shown to be generated by logarithmic loop corrections to the tree-level asymptotically shift-invariant potential in the non-minimal Higgs inflation model and R2-gravity. The solution to the problem of hierarchy between the Planckian scale and the inflation scale is discussed within the concept of conformal higher spin fields, which also suggests the mechanism bringing the model below the gravitational cutoff and, thus, protecting it from large graviton loop corrections.