9,235 research outputs found
Primordial gravitational wave of BICEP2 from dynamical double hybrid inflation
BICEP2 has observed a primordial gravitational wave corresponding to the
tensor-to-scalar ratio of 0.16. It seems to require a super-Planckian
inflationary model. In this paper, we propose a double hybrid inflation model,
where the inflaton potential dynamically changes with the evolution of the
inflaton fields. During the first phase of inflation over 7 e-folds, the power
spectrum can be almost constant by a large linear term in the hybrid potential,
which is responsible also for the large tensor-to-scalar ratio. In the second
phase of 50 e-folds, the dominant potential becomes dynamically changed to the
logarithmic form as in the ordinary supersymmetric hybrid inflation, which is
performed by the second inflaton field. In this model, the sub-Planckian field
values (~0.9 M_P) can still yield the correct cosmic observations with the
sufficient e-folds.Comment: 12 pages, 1 figure, version to appear in Phys. Lett.
X-ray line signal from decaying axino warm dark matter
We consider axino warm dark matter in a supersymmetric axion model with
R-parity violation. In this scenario, axino with the mass m_\axino\simeq 7
keV can decay into photon and neutrino resulting in the X-ray line signal at
keV, which might be the origin of unidentified X-ray emissions from
galaxy clusters and Andromeda galaxy detected by the XMM-Newton X-ray
observatory.Comment: 8 pages, 2 figures, typos corrected, discussion and one more figure
added, the final journal versio
Review of local non-Gaussianity from multi-field inflation
We review models which generate a large non-Gaussianity of the local form. We
first briefly consider three models which generate the non-Gaussianity either
at or after the end of inflation; the curvaton scenario, modulated (p)reheating
and an inhomogeneous end of inflation. We then focus on ways of generating the
non-Gaussianity during inflation. We derive general conditions which a product
or sum separable potential must satisfy in order to generate a large local
bispectrum during slow-roll inflation. As an application we consider two-field
hybrid inflation. We then derive a formalism not based on slow roll which can
be applied to models in which the slow-roll parameters become large before
inflation ends. An exactly soluble two-field model is given in which this
happens. Finally we also consider further non-Gaussian observables; a scale
dependence of f_NL and the trispectrum.Comment: 22 pages, 2 figures. Invited review for the special issue "Testing
the Gaussianity and Statistical Isotropy of the Universe" for Advances in
Astronomy. v2: Numerous references and comments adde
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