Searcharxiv⌕ Search

arXiv subjects

Eiichi Takasugi

Publications and source records attributed to Eiichi Takasugi.

At least 37 records · Page 2Linked to original sources
arXiv2000

Renormalization group effect and a democratic-type neutrino mass matrix

In our previous paper, we proposed the democratic-type neutrino mass matrix which gives interesting predictions, $θ_{23}=-\fracπ4$, $|\tan θ_{12}|=\sqrt{2-3\sin^2 θ_{13}}$ and $δ=\frac π2$, where $θ_{ij}$ is the mixing angle between mass eigenstates $ν_i$ and $ν_j$, and $δ$ is the CP violation angle in the standard parameterization of mixing matrix. In this paper, we examined how predictions behave at $m_Z$ by assuming that they are given at the right-handed neutrino mass scale, $M_R$.

hep-ph↗
arXiv2000

de Broglie-Bohm Interpretatin for Analytic Solutions of The Wheeler-DeWitt Equation in Spherically Symmetric Space-time

We discuss the implications of a wave function for quantum gravity, which involves nothing but 3-dimensional geometries as arguments and is invariant under general coordinate transformations. We derive an analytic wave function from the Wheeler-DeWitt equation for spherically symmetric space-time with the coordinate system arbitrary. The de Broglie-Bohm interpretation of quantum mechanics is applied to the wave function. In this interpretation, deterministic dynamics can be yielded from a wave function in fully quantum regions as well as in semiclassical ones. By introducing a coordinate system additionally, we obtain a cosmological black hole picture in compensation for the loss of general covariance. Our analysis shows that the de Broglie-Bohm interpretation gives quantum gravity an appropriate prescription to introduce coordinate systems naturally and extract information from a wave function as a result of breaking general covariance.

gr-qc↗
arXiv2000

Quantum effects for the neutrino mixing matrix in the democratic-type model

We investigate the quantum effects for the democratic-type neutrino mass matrix given at the right-handed neutrino mass scale $m_R$ in order to see (i) whether $θ_{23}=-π/4$ predicted by the model is stable to explain the atmospheric neutrino anomaly, (ii) how $θ_{12}$ and $θ_{13}$ behave, and (iii) whether the predicted Dirac CP phase $δ$ keeps maximal size, at the weak scale $m_Z$. We find that, for the (inversely) hierarchical mass spectrum with $m_1\sim m_2$, $θ_{23}$ and $θ_{13}$ are stable, while $θ_{12}$ is not so, which leads to the possibility that the solar neutrino mixing angle can become large at $m_Z$ even if it is taken small at $m_R$. We also show that $δ$ keeps almost maximal for the above mass spectrum, and our model can give the large CP violation effect in the future neutrino oscillation experiments if the solar neutrino puzzle is explained by the large mixing angle MSW solution.

hep-ph↗
arXiv2000

Democratic-type neutrino mass matrix

We consider the democratic-type neutrino mass matrix and show that this matrix predicts the atmospheric neutrino mixing to be almost maximal, $\sin^2 2θ_{atm}>0.999$ as well as the large CP violation (the CP violation phase in the standard form is maximal $δ=π/2$). We construct the $Z_3$ symmetric dimension five effective Lagrangian with two up-type Higgs doublets and show that this Lagrangian leads to the democratic neutrino mass matrix. Furthermore, we consider the restricted model with one up-type Higgs doublet and obtain the prediction, $0.87<\sin^2 2θ_{sol}<8/9$.

hep-ph↗
arXiv2000

Large CP Violation, Large Mixings of Neutrinos and the $Z_3$ Symmetry

We present neutrino mass matrices which predict the atmospheric neutrino mixing to be almost maximal, $\sin^2 2θ_{atm}>0.999$, as well as the large solar neutrino mixing, $8/9>\sin^2 2θ_{sol}>0.87$, and the large CP violation (the CP violation phase in the standard form is maximal $δ=π/2$), based on the $Z_3$ symmetry.

hep-ph↗
arXiv1999

Large CP Violation, Large Mixings of Neutrinos and Democratic-type Neutrino Mass Matrix

We propose a democratic-type neutrino mass matrix based on $Z_3$ symmetry. This mass matrix predicts the CP violation phase, $δ=π/2$, and the mixing angle between the mass eigenstates $ν_2$ and $ν_3$, $\sin^2 θ_{23}= \cos^2 θ_{23}=1/2$ which is essential for the large atmospheric neutrino mixing, between $ν_μ$ and $ν_τ$. In this model, the large CP violation effect may be expected.

hep-ph↗
arXiv1998

de Broglie-Bohm interpretation for wave function of Reissner-Nordstrom-de Sitter black hole

We study the canonical quantum theory of the Reissner-Nordstrom-de Sitter black hole(RNdS). We obtain an exact general solution of the Wheeler-DeWitt equation for the spherically symmetric geometry with electro-magnetic field. We investigate the wave function form a viewpoint of the de Broglie-Bohm interpretation. The de Broglie-Bohm interpretation introduces a rigid trajectory on the minisuperspace without assuming an outside observer or causing collapse of the wave function. In our analysis, we obtain the boundary condition for the wave function which corresponds to the classical RNdS black hole and describe the quantum fluctuations near the horizons quantitatively.

gr-qc↗
arXiv1998

Unified Explanation of Quark and Lepton Masses and Mixings in the Supersymmetric SO(10) Model

We discussed neutrino masses and mixings in SUSY SO(10) model where quarks and leptons have Yukawa couplings to at least two 10 and one $\bar{126}$ Higgs scalars. In this model, the Dirac and the right-handed Majorana mass terms are expressed by linear combinations of quark and charged lepton mass matrices, which then determine the neutrino mass matrix by the see-saw mechanism. We show that there are various solutions to reproduce a large mixing angle for $ν_μ-ν_τ$ and a small mixing angle for $ν_e-ν_μ$, as well as the hierarchical mass spectrum of neutrinos.

hep-ph↗
arXiv1998

Perturbations of Kerr-de Sitter Black Hole and Heun's Equations

It is well known that the perturbation equations of massless fields for the Kerr-de Sitter geometry can be written in the form of separable equations. The equations have five definite singularities so that the analysis has been expected to be difficult. We show that these equations can be transformed to Heun's equations, for which we are able to use known technique for the analysis of the solutions. We reproduce results known previously for the Kerr geometry and de Sitter geometry in the confluent limits of the Heun's functions. Our analysis applies can be extended to Kerr-Newman-de Sitter geometry for massless fields with spin 0 and 1/2.

gr-qc↗
arXiv1998

$e^- e^-$ Collisions Mediated by Composite Neutrinos

The lepton number violating process, $e^- e^- \to W^- W^-$ has been widely discussed in the Majorana neutrino exchange mechanism. Here, we discuss this process in a composite neutrino model where excited Majorana neutrinos are exchanged. We found several qualitatively different features from the neutrino exchange case: (1) The longitudinally polarized $W$'s are not produced, (2) the neutrinoless double beta decay does not constrain much and a much larger cross section is expected, and (3) CP violating phases may be explored because all excited neutrinos are heavy so that large mixings among them are expected.

hep-ph↗
arXiv1997

Post-Newtonian Expansion of Gravitational Waves from a Particle in Circular Orbits around a Rotating Black Hole :Effects of Black Hole Absorption

When a particle moves around a Kerr black hole, it radiates gravitational waves.Some of these waves are absorbed by the black hole. We calculate such absorption of gravitational waves induced by a particle of mass mu in a circular orbit on an equatorial plane around a Kerr black hole of mass M. We assume that the velocity of the particle v is much smaller than the speed of light c and calculate the energy absorption rate analytically. We adopt an analytic technique for the Teukolsky equation developed by Mano, Suzuki and Takasugi. We obtain the energy absorption rate to O((v/c)^8) compared to the lowest order. We find that the black hole absorption occurs at O((v/c)^5) beyond the Newtonian-quadrapole luminosity at infinity in the case when the black hole is rotating, which is O((v/c)^3) lower than the non-rotating case. Using the energy absorption rate, we investigate its effects on the orbital evolution of coalescing compact binaries.

gr-qc↗
arXiv1997

Reconstruction of quark mass matrices in the NNI form from the experimental data

We examined the question that what is a general form of quark mass matrices which is achieved by the transformation that leaves the left-handed gauge interaction invariant. In particular, we analyzed in detail the Fritzsch-type and the Branco-Silva-Marcos-type parametrization. Both parametrizations contain ten parameters and can be expressed by the experimental data. We explicitly reconstructed quark mass matrices in terms of quark masses and CKM parameters for the Fritzsch-type parametrization.

hep-ph↗
arXiv1997

Double Beta Decay Constraint on Composite Neutrinos

Neutrinoless double beta decay occurs through the magnetic coupling of dimension five, $λ_W/m_{ν*}$, among the excited electron neutrino $ν^*$, electron and $W$ boson if $ν^*$ is a massive Majorana neutrino. (λ_W m_W / m_{ν*}^2 |\frac{(m_*/m_W) +2}{(m_*/m_W +1)^2} -0.129{m_*/m_W} | <2.13\times 10^{-2}, where $λ_W$ is the relative strength, $m_{ν*}$ is the composite scale and $m_*$ is the mass of excited neutrino. If the coupling is not small, i.e., $λ_W>1$ and $m_{ν*}=m_*$, we find $m_*>3.4 m_W$.

hep-ph↗
arXiv1997

The rephasing freedom and the NNI form of quark mass matrices

For three generations of quarks, we show that one of quark mass matrices can be transformed into either a Fritzsch form or a Branco-Silva-Marcos form, while the other is kept in the NNI basis. In these bases, quark mass matrices are determined unambiguously once quark masses and the CKM mixing are given.

hep-ph↗
arXiv1996

Analytic Solutions of the Teukolsky Equation and their Properties

The analytical solutions reported in our previous paper are given as series of hypergeometric or Coulomb wave functions. By using them, we can get the Teukolsky functions analytically in a desired accuracy. For the computation, the deep understanding of their properties is necessary. We summarize the main result: The relative normalization between the solutions with a spin weight s and -s is given analytically by using the Teukolsky-Starobinsky (T-S) identities. By examining the asymptotic behaviors of our solution and combined with the T-S identities and the Wronskian, we found nontrivial identities between the sums of coefficients of the series. These identities will serve to make various expression in simpler forms and also become a powerful tool to test the accuracy of the computation. As an application, we investigated the absorption rate and the evaporation rate of black hole and obtain interesting analytic results.

gr-qc↗