arXiv subjects

Natsuki Watanabe

Publications and source records attributed to Natsuki Watanabe.

5 recordsLinked to original sources

arXiv2014

The f(R) Gravity Function of the Linde Quintessence

We calculate the f(R) gravity function in the dual gravity description of the quintessence model with a quadratic (Linde) scalar potential and a positive cosmological constant. We find that in the large curvature regime relevant to chaotic inflation in early Universe, the dual f(R) gravity is well approximated by the (matter) loop-corrected Starobinsky inflationary model. In the small curvature regime relevant to dark energy in the present Universe, the f(R) gravity function reduces to the Einstein-Hilbert one with a positive cosmological constant.

hep-th↗

arXiv2013

Domain wall in $f(R)$ gravity

The gravitational impact inside and outside of a domain wall is studied in the context of $f(R)$ gravity theory. The function $f(R)$ is found which satisfies the stability conditions. Our results imply that the domain wall may cause topological inflation.

gr-qc↗

arXiv2012

Dark Energy in Modified Supergravity

We propose a supersymmetric extension of the dynamical dark energy function and the corresponding scalar (super)potential in F(R) supergravity. Our model is viable in the Einstein approximation, and also has an analytic (regular) Wess-Zumino-type scalar superpotential. The hidden sector responsible for spontaneous supersymmetry breaking is given.

hep-th↗

arXiv2011

Cosmological constant in F(R) supergravity

A cosmological constant in the regime of low space-time curvature is calculated in the recently proposed version of F(R) supergravity with a generic cubic function F. The F(R) supergravity is the N=1 supersymmetric extension of f(R) gravity. The cubic model is known to successfully describe a chaotic (slow-roll) inflation in the regime of high space-time curvature. We find that a simple extension of the same model allows a positive cosmological constant in the regime of low space-time curvature. The inflaton superfield in F(R) supergravity (like inflaton in f(R) gravity) violates the Strong Energy Condition and thus breaks the restriction of the standard supergravity (with usual matter) that can only have either a negative or vanishing cosmological constant.

hep-th↗

arXiv2011

Cosmological properties of a generic (\cal R)^2-supergravity

We investigate in detail the structure of the simplest non-trivial F(\cal R)-supergravity model, whose F-function is given by a generic quadratic polynomial in terms of the scalar supercurvature (\cal R). This toy-model admits a fully explicit derivation of the corresponding f(R)-gravity functions. We apply the stability conditions for selecting the physical f(R)-gravity functions, and discuss the phenomenological prospects of F(\cal R)-supergravity in its application to cosmology.

hep-th↗