Neutrino mixing in Seesaw model

We study the neutrino mixing matrix (the MNS matrix) in the seesaw model. By assuming a large mass hierarchy for the heavy right-handed Majorana mass, we show that, in the diagonal Majorana base, the MNS matrix is determined by a unitary matrix, $S$, which transforms the neutrino Yukawa matrix, $y_{\nu}$, into a triangular form, $y_{\triangle}$. The mixing matrix of light leptons is $V_{KM} S^{\prime *}$, where $V_{KM} \equiv {V_{Le}}^{\dagger} V_{L \nu}$ %$V_{Le}$ and $V_{L\nu}$ diagonalize %the Yukawa matrices of charged leptons, %$y_e y_e^{\dagger}$, and neutrinos, $y_{\nu} y_{\nu}^{\dagger}$, %respectively, and $S^{\prime *} \equiv {V_{L\nu}}^{\dagger} S^*$. Large mixing may occur without fine tuning of the matrix elements of $y_{\triangle}$ even if the usual KM-like matrix $V_{KM}$ is given by $V_{KM} =1$. This large mixing naturally may satisfy the experimental lower bound of the mixing implied by the atmospheric neutrino oscillation.Comment: 14 pages, 4 figures, PTPTe

Thermal Restoration of Chiral Symmetry in Supersymmetric Nambu-Jona-Lasinio Model with Soft SUSY Breaking

The supersymmetric version of the Nambu-Jona-Lasinio model is investigated in connection with the chiral symmetry breaking induced by a soft SUSY breaking term. It is found that the broken chiral symmetry due to the soft breaking term is restored at suitably high temperature and the symmetry restoration occurs as first-order phase transitions. The critical temperature at which the chiral symmetry is restored is determined as a function of the strength of the soft breaking term and the field coupling constant. The dynamical fermion mass is calculated at finite temperature. Some possible applications to the breaking scenario of unified field theories are discussed.Comment: 9 pages, 2 figure

Numerical study on the correlation between CP violation in neutrino oscillations and baryogenesis

We numerically study the correlation between CP violation in the neutrino oscillations and baryogenesis in the seesaw model. In this study we get the heavy Majorana neutrino masses and lepton number asymmetries from their decays by fitting the data of neutrino oscillations and by working on some hypothesis of the Dirac-Yukawa term for neutrinos.Comment: 3 pages, 2 figures, Latex, presented at KEKTC5(Nov. 2001), to be published in Nucl. Phys. Proc. Supp

Pattern of Chiral Symmetry Restoration at Finite Temperature in A Supersymmetric Composite Model

The structure of chiral symmetry restorations at finite temperature is thoroughly investigated in the supersymmetric Nambu-Jona-Lasinio model with a soft supersymmetry breaking term. It is found that the broken chiral symmetry at vanishing temperature is restored at sufficiently high temperature in two patterns, i. e., the first order and second order phase transition depending on the choice of the coupling constant $G$ and the supersymmetry breaking parameter $\Delta$. The critical curves expressing the phase boundaries in the $G-\Delta$ plane are completely determined and the dynamically generated fermion mass is calculated as a function of temperature.Comment: 12 pages, 4 figures, REVTe

Curvature-induced phase transitions in the inflationary universe - Supersymmetric Nambu-Jona-Lasinio Model in de Sitter spacetime -

The phase structure associated with the chiral symmetry is thoroughly investigated in de Sitter spacetime in the supersymmetric Nambu-Jona-Lasinio model with supersymmetry breaking terms. The argument is given in the three and four space-time dimensions in the leading order of the 1/N expansion and it is shown that the phase characteristics of the chiral symmetry is determined by the curvature of de Sitter spacetime. It is found that the symmetry breaking takes place as the first order as well as second order phase transition depending on the choice of the coupling constant and the parameter associated with the supersymmetry breaking term. The critical curves expressing the phase boundary are obtained. We also discuss the model in the context of the chaotic inflation scenario where topological defects (cosmic strings) develop during the inflation.Comment: 29 pages, 6 figures, REVTe

A relation between CP violation of low energy and leptogenesis

We discuss how CP violation generating lepton number asymmetry can be related to CP violation in low energy.Comment: A poster Talk presented at KEKTC5, submitted to the proceeding

New Development of the J -Based Fracture Testing Technique for Ceramic-Matrix Composites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65733/1/j.1151-2916.1994.tb09756.x.pd

A Model of Curvature-Induced Phase Transitions in Inflationary Universe

Chiral phase transitions driven by space-time curvature effects are investigated in de Sitter space in the supersymmetric Nambu-Jona-Lasinio model with soft supersymmetry breaking. The model is considered to be suitable for the analysis of possible phase transitions in inflationary universe. It is found that a restoration of the broken chiral symmetry takes place in two patterns for increasing curvature : the first order and second order phase transition respectively depending on initial settings of the four-body interaction parameter and the soft supersymmetry breaking parameter. The critical curves expressing the phase boundaries in these parameters are obtained. Cosmological implications of the result are discussed in connection with bubble formations and the creation of cosmic strings during the inflationary era.Comment: 12 pages, 3 figures, REVTe

Analytical modelling of the formation temperature stabilization during the borehole shut-in period

The problem of formation temperature stabilization during the shut-in period is solved analytically by the approximate generalized integral-balance method. The model accounts for the thermal history of the borehole exploitation, which may include a finite number of circulation and shut-in periods, and different flow regimes during circulation periods. The latter is determined by the temperatures of the circulating fluid and different Biot numbers that depend on intensity of the heat transfer on the bore-face. Normally the temperature fields in the well and surrounding rocks are calculated numerically by the finite-difference and finite-element methods or analytically, by applying the Laplace-transform method. Formulae, analytically obtained by Laplace transform, are rather bulky and require tedious non-trivial numerical evaluations. Moreover, in previous research the heat interactions of the circulating fluid with formation were treated under the condition of constant bore-face temperatures. In the present study the temperature field in the formation disturbed by the heat flow from the borehole is modelled by the heat conduction equation and thermal interaction of the circulating fluid with formation is approximated by the Newton relationship on the bore-face. The problem for circulation and shut-in periods is solved analytically using the heat balance integral method, where the radius of thermal influence, which defines the thermally disturbed domain, is a function of time, which satisfies the algebraic equation. Within this method, the approximate solution of the heat conduction problem is sought in the form of a finite sum of functions which belong to a complete set of the linearly independent functions defined on the finite interval bounded by the radius of thermal influence and satisfy the homogeneous boundary condition on the bore-face. It can be proved theoretically that the approximate solution found by this method converges to the exact one. Numerical results illustrate quite good agreement between the approximate and exact solutions. As a result of its simplicity and accuracy, the derived solution is convenient for geophysical practitioners and can be readily used, for instance, for predicting equilibrium formation temperatures