Scalaron from R2-gravity as a heavy field

By Shi Pi, Ying-li Zhang, Q. Huang, Misao Sasaki. 2017

288 citations recorded by the source corpus.

We study a model of inflation in which a scalar field χ is non-minimally coupled to Starobinsky's R2 gravity. After transforming it to the Einstein frame, a new scalar field, the scalaron ϕ, will appear and couple to χ with a nontrivial field metric, while χ acquires a positive mass via the non-minimal coupling. Initially inflation occurs along the ϕ direction with χ trapped near its origin by this induced mass. After ϕ crosses a critical value, it starts rolling down rapidly and proceeds to damped oscillations around an effective local minimum determined by the value of χ, while inflation still continues, driven by the χ field at this second stage where the effect of the non-minimal coupling becomes negligible. The presence of the damped oscillations during the transition from the first to second stage of inflation causes enhancement and oscillation features in the power spectrum of the curvature perturbation. Assuming that the oscillations may be treated perturbatively, we calculate these features by using the δ N formalism, and discuss its observational implications to large scale CMB anomalies or primordial black hole formation, depending on the scale of the features.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Oceanography

View Paper: https://www.semanticscholar.org/paper/56f97672cf86e8e67d38d48f24c3c23b82423c0f

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Citations in the corpus

Generating PBHs and small-scale GWs in two-field models of inflation (2020, methodology): “Among these we mention hybrid inflationary models, where a second waterfall field triggers the growth of fluctuations near to the end of inflation [33–37], models with couplings of the inflaton to scalaron fields [32, 38, 39] or with explosive production of gauge fields [40–42].”