893 research outputs found
Inflationary cosmology in modified gravity theories
We review inflationary cosmology in modified gravity such as gravity
with its extensions in order to generalize the Starobinsky inflation model. In
particular, we explore inflation realized by three kinds of effects:
modification of gravity, the quantum anomaly, and the term in loop
quantum cosmology. It is explicitly demonstrated that in these inflationary
models, the spectral index of scalar modes of the density perturbations and the
tensor-to-scalar ratio can be consistent with the Planck results. Bounce
cosmology in gravity is also explained.Comment: 24 pages, no figure, invited review to appear in Symmetr
Reconstruction of scalar field theories realizing inflation consistent with the Planck and BICEP2 results
We reconstruct scalar field theories to realize inflation compatible with the
BICEP2 result as well as the Planck. In particular, we examine the chaotic
inflation model, natural (or axion) inflation model, and an inflationary model
with a hyperbolic inflaton potential. We perform an explicit approach to find
out a scalar field model of inflation in which any observations can be
explained in principle.Comment: 7 pages, no figure, version accepted for publication in Physics
Letters
One-loop Modified Gravity in de Sitter Universe, Quantum Corrected Inflation, and its Confrontation with the Planck Result
Motivated by issues on inflation, a generalized modified gravity model is
investigated, where the model Lagrangian is described by a smooth function
of the Ricci scalar , the kinetic term of a scalar field
. In particular, the one-loop effective action in the de Sitter
background is examined on-shell as well as off-shell in the Landau gauge. In
addition, the on-shell quantum equivalence of gravity in the Jordan and
Einstein frames is explicitly demonstrated. Furthermore, we present
applications related to the stability of the de Sitter solutions and the
one-loop quantum correction to inflation in quantum-corrected gravity. It
is shown that for a certain range of parameters, the spectral index of the
curvature perturbations can be consistent with the Planck analysis, but the
tensor-to-scalar ratio is smaller than the minimum value within the 1
error range of the BICEP2 result.Comment: 21 pages, no figure, several references adde
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