Instanton Correction of Prepotential in Ruijsenaars Model Associated with N=2 SU(2) Seiberg-Witten Theory

Instanton correction of prepotential of one-dimensional SL(2) Ruijsenaars model is presented with the help of Picard-Fuchs equation of Pakuliak-Perelomov type. It is shown that the instanton induced prepotential reduces to that of the SU(2) gauge theory coupled with a massive adjoint hypermultiplet.Comment: revtex, 15 pages, to be published in Journal of Mathematical Physic

Double Exchange Ferromagnetism in the Peierls Insulator State

We study the effects of opening of the band gap on the double exchange ferromagnetism. Applying the density-matrix renormalization group method and an analytical expansion from the dimer limit to the one-dimensional double exchange model, we demonstrate for a relevant region of the exchange coupling that, in the weak dimerization regime, the Peierls gap opens in the fully spin-polarized conduction band without affecting its ferromagnetism, whereas in the strong dimerization regime, the ferromagnetism is destroyed and the Mott gap opens instead, leading the system to the antiferromagnetic quasi-long-range order. An insulator version of the double exchange ferromagnetism is thus established.Comment: 5 pages, 3 figures, Phys. Rev. Lett., in pres