Is Ue3U_{e3} really related to the solar neutrino solutions?

It has been said that the measurements of $U_{e3}$ in the lepton flavor mixing matrix would help discriminate between the possible solar neutrino solutions under the natural conditions with the neutrino mass hierarchies of $m_1 \ll m_2 \ll m_3$ and $m_1 \sim m_2 \gg m_3$, where $m_i$ is the $i$-th generation neutrino absolute mass. However, it is not true, and the relation between $\sin^2 2 \theta_{12}$ and $U_{e3}$ obtained by Akhmedov, Branco, and Rebelo is trivial in actual. We show in this paper that the value of $U_{e3}$ cannot predict the solar neutrino solutions without one additional nontrivial condition.Comment: 7pages, no figur

Electron-capture Supernovae of Super-AGB Stars: Sensitivity on Input Physics

Stars of M ~ 8–10 M⊙ on their main sequence form strongly electron-degenerate oxygen–neon–magnesium (ONeMg) cores and become super–asymptotic giant branch stars. If such an ONeMg core grows to 1.38 M⊙, electron captures on ²⁰Ne(e, ν_e) ²⁰F(e, ν_e) ²⁰O take place and ignite O–Ne deflagration around the center. In this work, we perform two-dimensional hydrodynamical simulations of the propagation of the O–Ne flame to see whether such a flame triggers a thermonuclear explosion or induces a collapse of the ONeMg core due to subsequent electron capture behind the flame. We present a series of models to explore how the outcome depends on model parameters for a central density ranging between 10^(9.80) and 10^(10.20) g cm⁻³, flame structures of both centered and off-centered ignition kernels, special and general relativistic effects, turbulent flame speed formulae, and the treatments of laminar burning phase. We obtain bifurcation between the electron-capture induced collapse and thermonuclear explosion depending mainly on the central density. We find that the ONeMg core obtained from stellar evolutionary models has a high tendency to collapse into a neutron star. We discuss the implications of the electron-capture supernovae in chemical evolution and the possible observational signals of this class of supernovae

The neutrinoless double β\beta decay and the neutrino mass hierarchy

Recently the evidence of the neutrinoless double $\beta$ ($0\nu \beta\beta$) decay has been announced. This means that neutrinos are Majorana particles and their mass hierarchy is forced to certain patterns in the diagonal basis of charged lepton mass matrix. We estimate the magnitude of $0\nu \beta\beta$ decay in the classification of the neutrino mass hierarchy patterns as Type A, $m_{1,2} \ll m_{3}$, Type B, $m_1 \sim m_2 \gg m_3$, and Type C, $m_1 \sim m_2 \sim m_3$, where $m_{i}$ is the $i$-th generation neutrino absolute mass. The data of $0\nu \beta\beta$ decay experiment suggests the neutrino mass hierarchy pattern should be Type B or C. Type B predicts a small magnitude of $0\nu \beta\beta$ decay which is just edge of the allowed region of experimental value in $95$, where Majorana CP phases should be in a certain parameter region. Type C can induce the suitably large amount of $0\nu \beta\beta$ decay which is consistent with the experimental data, where overall scale of degenerate neutrino mass plays a crucial role, and its large value can induce the large $0\nu \beta\beta$ decay in any parameter regions of Majorana CP phases.Comment: 12 pages, 7 figures, LaTe

The Connection between Gamma-Ray Bursts and Extremely Metal-Poor Stars: Black Hole-forming Supernovae with Relativistic Jets

Long-duration gamma-ray bursts (GRBs) are thought to be connected to luminous and energetic supernovae (SNe), called hypernovae (HNe), resulting from the black-hole (BH) forming collapse of massive stars. For recent nearby GRBs~060505 and 060614, however, the expected SNe have not been detected. The upper limits to the SN brightness are about 100 times fainter than GRB-associated HNe (GRB-HNe), corresponding to the upper limits to the ejected $^{56}$Ni masses of $M({\rm ^{56}Ni})\sim 10^{-3}M_\odot$. SNe with a small amount of $^{56}$Ni ejection are observed as faint Type II SNe. HNe and faint SNe are thought to be responsible for the formation of extremely metal-poor (EMP) stars. In this Letter, a relativistic jet-induced BH forming explosion of the 40 $M_\odot$ star is investigated and hydrodynamic and nucleosynthetic models are presented. These models can explain both GRB-HNe and GRBs without bright SNe in a unified manner. Their connection to EMP stars is also discussed. We suggest that GRBs without bright SNe are likely to synthesize \Mni\sim 10^{-4} to $10^{-3}M_\odot$ or $\sim 10^{-6}M_\odot$.Comment: 7 pages, 3 figures. Accepted for publication in the Astrophysical Journal Letters (10 March 2007, v657n2 issue