Magnon scattering processes and low temperature resistivity in CMR manganites

Low temperature resistivity of CMR manganites is investigated. At the ground state, conduction electrons are perfectly spin polarized, which is called half-metallic. From one-magnon scattering processes, it is discussed that the resistivity of a half metal as a function of temperature scales as rho(T) - rho(0) propto T^3. We take (Nd,Tb,Sr)MnO_3 as an example to compare theory and experiments. The result is in a good agreement.Comment: To appear in Proc. ICM 200

Model building by coset space dimensional reduction in ten-dimensions with direct product gauge symmetry

We investigate ten-dimensional gauge theories whose extra six-dimensional space is a compact coset space, $S/R$, and gauge group is a direct product of two Lie groups. We list up candidates of the gauge group and embeddings of $R$ into them. After dimensional reduction of the coset space,we find fermion and scalar representations of $G_{\mathrm{GUT}} \times U(1)$ with $G_{\mathrm{GUT}}=SU(5), SO(10)$ and $E_6$ which accomodate all of the standard model particles. We also discuss possibilities to generate distinct Yukawa couplings among the generations using representations with a different dimension for $G_{\mathrm{GUT}}=SO(10)$ and $E_6$ models.Comment: 14 pages; added local report number, added refferenc

On the Logarithmic Asymptotics of the Sixth Painleve' Equation (Summer 2007)

We study the solutions of the sixth Painlev\'e equation with a logarithmic asymptotic behavior at a critical point. We compute the monodromy group associated to the solutions by the method of monodromy preserving deformations and we characterize the asymptotic behavior in terms of the monodromy itself.Comment: LaTeX with 8 figure