| 研究実績の概要 |
The R2 inflation which is an extension of general relativity (GR) by quadratic scalar curvature introduces a quasi-de Sitter expansion of the early Universe governed by Ricci scalar being an eigenmode of d’Alembertian operator. He derived a most general theory of gravity admitting R2 inflationary solution which turned out to be higher curvature non-local extension of GR. He studied in detail inflationary perturbations in this theory and analysed the structure of form factors that leads to a massive scalar (scalaron) and massless tensor degrees of freedom. He argued that the theory contains only finite number of free parameters which can be fixed by cosmological observations. He derived predictions of our generalized non-local R2-like inflation and obtain the scalar spectral index ns is 1 - 2/N and any value of the tensor-to-scalar ratio r < 0.036. In this theory, tensor spectral index can be either positive or negative and the well-known consistency relation is violated in a non-trivial way. He also computed running of the tensor spectral index and discussed observational implications to distinguish this model from several classes of scalar field models of inflation. These predictions allow us to probe the nature of quantum gravity in the scope of future CMB and gravitational wave observations.
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