arXiv subjects

Tsutomu Takayama

Publications and source records attributed to Tsutomu Takayama.

5 recordsLinked to original sources

arXiv2009

Leptogenesis Scenarios via Non-Thermally Produced Right-handed Neutrino and Sneutrino in Supersymmetric Seesaw Model

We reconsidered leptogenesis scenario from right-handed (s)neutrino produced by the decay of inflaton. Besides the well-investigated case that the neutrino decays instantaneously after the production, leptogenesis is possible if neutrino decays after it dominates the universe. In the latter case, right-handed (s)neutrino can decay either while it is relativistic or after it becomes non-relativistic. Especially, the first case has not been discussed seriously in literatures. Resultant lepton asymmetry and constraints from the gravitino problem are studied in broad parameter region, including all cases of this scenario. It is also shown how this leptogenesis scenario depends on the parameters, the inflaton decay rate (the reheating temperature), the right-handed neutrino mass, the washout parameter, and the constraint from the gravitino problem. Leptogenesis from relativistic neutrino decay is interesting because both thermal and non-thermal gravitino problems can be relaxed.

hep-ph↗

arXiv2008

Formation of intermediate-mass black holes as primordial black holes in the inflationary cosmology with running spectral index

Formation of primordial black holes (PBHs) on astrophysical mass scales is a natural consequence of inflationary cosmology if the primordial perturbation spectrum has a large and negative running of the spectral index as observationally inferred today, because double inflation is required to explain it and fluctuations on some astrophysical scales are enhanced in the field oscillation regime in between. It is argued that PBHs thus produced can serve as intermediate-mass black holes (IMBHs) which act as the observed ultraluminous X-ray sources (ULXs) by choosing appropriate values of the model parameters in their natural ranges. Our scenario can be observationally tested in near future because the mass of PBHs is uniquely determined once we specify the values of the spectral index and its running on large scales.

astro-ph↗

arXiv2007

Affleck-Dine leptogenesis via multiscalar evolution in a supersymmetric seesaw model

A leptogenesis scenario in a supersymmetric standard model extended with introducing right-handed neutrinos is reconsidered. Lepton asymmetry is produced in the condensate of a right-handed sneutrino via the Affleck-Dine mechanism. The LH_u direction develops large value due to a negative effective mass induced by the right-handed sneutrino condensate through the Yukawa coupling of the right-handed neutrino, even if the minimum during the inflation is fixed at the origin. The lepton asymmetry is nonperturbatively transfered to the LH_u direction by this Yukawa coupling.

hep-ph↗

arXiv2007

Power Spectrum of the Density Perturbations From Smooth Hybrid New Inflation Model

We numerically investigate density perturbations generated in the smooth hybrid new inflation model, a kind of double inflation model that is designed to reproduce the running spectral index suggested by the WMAP results. We confirm that this model provides the running spectral index within 1sigma range of the three year WMAP result. In addition, we find a sharp and strong peak on the spectrum of primordial curvature perturbation at small scales. This originates from amplification of fluctuation in the first inflaton fields due to parametric resonance, which takes place in the oscillatory phase between two inflationary regime. Formation probability of primordial black holes (PBHs) is discussed as a consequence of such peak.

hep-ph↗

arXiv2007

Baryogenesis via left-right asymmetry generation by Affleck-Dine mechanism in Dirac neutrino model

A baryogenesis scenario in supersymmetric standard models with Dirac neutrinos proposed by Abel and Page is reconsidered with introducing intermediate scale physics to stabilize the runaway potential along a right-handed sneutrino direction. In contrary with previous results, the baryon number asymmetry can be explained even for higher reheating temperature without entropy production if the lightest neutrino mass is small and/or thermal effects induce early oscillation. We discuss the solution to the problem of dark matter overproduction by the right-handed sneutrino decay by SU(2)_R gauge interaction.

hep-ph↗