#### Filter Results:

#### Publication Year

1995

2009

#### Publication Type

#### Co-author

#### Publication Venue

#### Key Phrases

Learn More

- H. P. Nilles, M. Yamaguchi
- 1997

We investigate gaugino condensation in the framework of the strongly coupled heterotic E 8 × E 8 string (M–theory). Supersymmetry is broken in a hidden sector and gravitational interactions induce soft breaking parameters in the observable sector. The resulting soft masses are of order of the gravitino mass. The situation is similar to that in the weakly… (More)

- H. P. Nilles, M. Yamaguchi
- 1998

We consider hidden sector supersymmetry breakdown in the strongly coupled heterotic E 8 × E 8 theory of Hořava and Witten. Using effective field theory methods in four dimensions, we can show that gravitational interactions induce soft breaking terms in the observable sector that are of order of the gravitiono mass. We apply these methods to the mechanism… (More)

We propose a chaotic inflation model in supergravity. In the model the Kähler potential has a Nambu-Goldstone-like shift symmetry of the inflaton chiral multiplet which ensures the flatness of the inflaton potential beyond the Planck scale. We show that the chaotic inflation naturally takes place by introducing a small breaking term of the shift symmetry in… (More)

Recently, a novel class of models for inflation has been found in which the inflationary dynamics is driven solely by (non-canonical) kinetic terms rather than by potential terms. As an obvious extension, we show that a scalar field with non-canonical kinetic terms alone behaves like an energy component which is time-varying and has negative pressure… (More)

- J. Hisano, T. Moroi, K. Tobe, M. Yamaguchi
- 1995

Various lepton-flavor violating (LFV) processes in the supersymmetric standard model with right-handed neutrino supermultiplets are investigated in detail. It is shown that large LFV rates are obtained when tan β is large. In the case where the mixing matrix in the lepton sector has a similar structure as the Kobayashi-Maskawa matrix and the… (More)

We study non-Gaussianity, the spectral index of primordial scalar fluctuations and tensor modes in models where fluctuations from the inflaton and the curvaton can both contribute to the present cosmic density fluctuations. Even though simple single-field inflation models generate only tiny non-Gaussianity, if we consider such a mixed scenario, large… (More)

We propose a self-consistent scenario of new inflation in supergravity. Chaotic inflation first takes place around the Planck scale, which solves the longevity problem, namely, why the universe can live much beyond the Planck time, and also gives an adequate initial condition for new inflation. Then, new inflation lasts long enough to generate primordial… (More)

- Chiaki Hikage, Kazuya Koyama, Takahiko Matsubara, Tomo Takahashi, Masahide Yamaguchi
- 2009

We study the effect of primordial isocurvature perturbations on non-Gaussian properties in CMB temperature anisotropies. We consider generic forms of the non-linearity of isocurvature perturbations which can be applied to a wide range of theoretical models. We derive analytical expressions of the bispectrum and the Minkowski Func-tionals for CMB temperature… (More)

We comprehensively investigate a chaotic inflation model proposed recently in the framework of supergravity. In this model, the form of Kähler potential is determined by a symmetry, that is, the Nambu-Goldstone like shift symmetry, which guarantees the absence of the exponential factor in the potential for the inflaton field. Though we need introduction of… (More)

- Tony Gherghetta, Kenji Kadota, Masahide Yamaguchi
- 2008

We show how leptogenesis can occur at the TeV scale with neutrinos that possess almost purely Dirac masses and negligible Majorana mass contributions as a consequence of the small wavefunction overlap in a warped fifth dimension. Lepton number violation at the Planck scale is introduced via a Majorana mass term on the Planck brane. Such a Majorana mass… (More)