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

Cross-Border Political Donations and Pareto-Efficient Tariffs

This paper examines the effects of lobbying activities across international borders, on determining each country’s import tariff in a multi-principal, multi-agent, menu-auction model. Cross-border political donations could promote international policy cooperation because of two of their distinctive characteristics. First, special interest groups use cross-border donations as tools to wield their influence on ruling parties of other countries directly, which promotes efficiency of policy formation. Second, for ruling parties of countries, cross-border donations make them take into account the impact of their policy on other countries, which makes them more sensitive to other countries’ welfare and, therefore, more cooperative with others. When ruling parties estimate the worth of political contributions from national special interest groups and from foreign lobbying groups with the same weight, Pareto-efficient tariffs are attained at which world welfare is maximized.Cross-border Donations, Truthful Equilibrium, Pareto-Efficient Tariffs

Leptogenesis and Low energy CP violation, a link

How is CP violation of low energy related to CP violation required from baryon number asymmetry ? We give an example which shows a direct link between CP violation of neutrino oscillation and baryogenesis through leptogenesis.Comment: 3 pages and 2 figures, Talk presented at 4th Nufac02, July 1-6, 200

Primordial Lepton Family Asymmtries in Seesaw Model

In leptogenesis scenario, the decays of heavy Majorana neutrinos generate lepton family asymmetries, $Y_e, Y_{\mu}$ and $Y_{\tau}$. They are sensitive to CP violating phases in seesaw models. The time evolution of the lepton family asymmetries are derived by solving Boltzmann equations. By taking a minimal seesaw model, we show how each family asymmetry varies with a CP violating phase. For instance, we find the case that the lepton asymmetry is dominated by $Y_{\mu}$ or $Y_{\tau}$ depending on the choice of the CP violating phase. We also find the case that the signs of lepton family asymmetries $Y_{\mu}$ and $Y_{\tau}$ are opposite each other. Their absolute values can be larger than the total lepton asymmetry and the baryon asymmetry may result from the cancellation of the lepton family asymmetries.Comment: 26 pages, 8 figures, ptp.styl

Can a Preferential Trade Agreement Benefit Neighbor Countries without Compensating Them?

PTAs are generally negotiated without any tariff concessions or transfers to non-member countries. Can such a PTA benefit the neighbors’ welfare? In a two-good competitive equilibrium model in the absence of an entrepot, a PTA without concessions to the outsider will hurt the outsider’s welfare when goods are normal. If one of the member countries is an entrepot, however, it definitely improves the neighbors’ welfare. In a multiple-good model, a PTA without concessions deteriorates the neighbors’ welfare, provided that all the goods are normal and substitutes, and that initial tariff levels are small.PTA, Neighbor’s Welfare, Kemp-Wan theorem, WTO, GATT Article 24, Entrepot

Three Dimensional Heisenberg Spin Glass Models with and without Random Anisotropy

We reexamine the spin glass (SG) phase transition of the $\pm J$ Heisenberg models with and without the random anisotropy $D$ in three dimensions ($d = 3$) using complementary two methods, i.e., (i) the defect energy method and (ii) the Monte Carlo method. We reveal that the conventional defect energy method is not convincing and propose a new method which considers the stiffness of the lattice itself. Using the method, we show that the stiffness exponent $\theta$ has a positive value ($\theta > 0$) even when $D = 0$. Considering the stiffness at finite temperatures, we obtain the SG phase transition temperature of $T_{\rm SG} \sim 0.19J$ for $D = 0$. On the other hand, a large scale MC simulation shows that, in contrary to the previous results, a scaling plot of the SG susceptibility $\chi_{\rm SG}$ for $D = 0$ is obtained using almost the same transiton temperature of $T_{\rm SG} \sim 0.18J$. Hence we believe that the SG phase transition occurs in the Heisenberg SG model in $d = 3$.Comment: 15 pages, 9 figures, to be published in J. Phys.