Non-thermal Leptogenesis and a Prediction of Inflaton Mass in a Supersymmetric SO(10) Model

The gravitino problem gives a severe constraint on the thermal leptogenesis scenario. This problem leads us to consider some alternatives to it if we try to keep the gravitino mass around the weak scale $m_{3/2} \sim 100$ GeV. We consider, in this paper, the non-thermal leptogenesis scenario in the framework of a minimal supersymmetric SO(10) model. Even if we start with the same minimal SO(10) model, we have different predictions for low-energy phenomenologies dependent on the types of seesaw mechanism. This is the case for leptogenesis: it is shown that the type-I see-saw model gives a consistent scenario for the non-thermal leptogenesis but not for type-II. The predicted inflaton mass needed to produce the observed baryon asymmetry of the universe is found to be $M_I \sim 5 \times 10^{11}$ GeV for the reheating temperature $T_R = 10^6$ GeV.Comment: 9 pages, 2 figures; the version to appear in JCA

Anomalous Hall effect and weak localization corrections in a ferromagnet

In this paper, we report results on the anomalous Hall effect. First, we summarize analytical calculations based on the Kubo formalism : explicit expressions for both skew-scattering and side-jump are derived and weak-localization corrections are discussed. Next, we present numerical calculations of the anomalous Hall resistivity based on the Dirac equation. Qualitative agreement with experiments is obtained.Comment: Proceeding JEMS'0

Effect of Local Inhomogeneity on Nucleation; Case of Charge Density Wave Depinning

The spatial inhomogeneities are expected to affect nucleation process in an essential way. These effects are studied theoretically by considering the case of the depinning of the charge density wave as a typical example. The threshold field of the depinning of the one-dimensional commensurate charge density wave with one impurity has been examined classically based on the phase Hamiltonian at absolute zero. It is found that the threshold field is lowered by a finite amount compared to that in the absence of an impurity.Comment: pages 12, LaTeX, 9 figures, uses jpsj.sty, submitted to J. Phys. Soc. Jp

Superconducting quantum phase transitions tuned by magnetic impurity and magnetic field in ultrathin a-Pb films

Superconducting quantum phase transitions tuned by disorder (d), paramagnetic impurity (MI) and perpendicular magnetic field (B) have been studied in homogeneously disordered ultrathin a-Pb films. The MI-tuned transition is characterized by progressive suppression of the critical temperature to zero and a continuous transition to a weakly insulating normal state with increasing MI density. In all important aspects, the d-tuned transition closely resembles the MI-tuned transition and both appear to be fermionic in nature. The B-tuned transition is qualitatively different and probably bosonic. In the critical region it exhibits transport behavior that suggests a B-induced mesoscale phase separation and presence of Cooper pairing in the insulating state.Comment: 17 pages, 4 figure

Field-controlled phase separation at the impurity-induced magnetic ordering in the spin-Peierls magnet CuGeO3

The fraction of the paramagnetic phase surviving at the impurity-induced antiferromagnetic order transition of the doped spin-Peierls magnet Cu(1-x)Mg(x)GeO3 (x < 5%) is found to increase with an external magnetic field. This effect is qualitatively explained by the competition of Zeeman energy and exchange interaction between local antiferromagnetic clustersComment: 4 pages 4 figure

Low Energy Properties of the Random Spin-1/2 Ferromagnetic-Antiferromagnetic Heisenberg Chain

The low energy properties of the spin-1/2 random Heisenberg chain with ferromagnetic and antiferromagnetic interactions are studied by means of the density matrix renormalization group (DMRG) and real space renormalization group (RSRG) method for finite chains. The results of the two methods are consistent with each other. The deviation of the gap distribution from that of the random singlet phase and the formation of the large-spin state is observed even for relatively small systems. For a small fraction of the ferromagnetic bond, the effect of the crossover to the random singlet phase on the low temperature susceptibility and specific heat is discussed. The crossover concentration of the ferromagnetic bond is estimated from the numerical data.Comment: 11 pages, revtex, figures upon reques