254 citations · 1.8k across the 51 of their papers we have counts for
5 papers · 1 filter
Degenerate spectrum in the neutrino mass anarchy with Wishart matrices and implications for and
Kwang Sik Jeong, Naoya Kitajima, Fuminobu Takahashi
We show that a degenerate neutrino mass spectrum can be realized in the neutrino mass anarchy hypothesis, if the neutrino Yukawa and right-handed neutrino mass matrices are given b…
Resonant conversions of QCD axions into hidden axions and suppressed isocurvature perturbations
Naoya Kitajima, Fuminobu Takahashi
We study in detail MSW-like resonant conversions of QCD axions into hidden axions, including cases where the adiabaticity condition is only marginally satisfied, and where anharmon…
Hidden axion dark matter decaying through mixing with QCD axion and the 3.5 keV X-ray line
Tetsutaro Higaki, Naoya Kitajima, Fuminobu Takahashi
Hidden axions may be coupled to the standard model particles through a kinetic or mass mixing with QCD axion. We study a scenario in which a hidden axion constitutes a part of or t…
Thermal Effects and Sudden Decay Approximation in the Curvaton Scenario
Naoya Kitajima, David Langlois, Tomo Takahashi +2
We study the impact of a temperature-dependent curvaton decay rate on the primordial curvature perturbation generated in the curvaton scenario. Using the familiar sudden decay appr…
Relaxing Isocurvature Bounds on String Axion Dark Matter
Masahiro Kawasaki, Naoya Kitajima, Fuminobu Takahashi
If inflation scale is high, light scalars acquire large quantum fluctuations during inflation.If sufficiently long-lived, they will give rise to CDM isocurvature perturbations, whi…