19,695 research outputs found

    Spontaneous Z2 Symmetry Breaking in the Orbifold Daughter of N=1 Super Yang-Mills Theory, Fractional Domain Walls and Vacuum Structure

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    We discuss the fate of the Z2 symmetry and the vacuum structure in an SU(N)xSU(N) gauge theory with one bifundamental Dirac fermion. This theory can be obtained from SU(2N) supersymmetric Yang--Mills (SYM) theory by virtue of Z2 orbifolding. We analyze dynamics of domain walls and argue that the Z2 symmetry is spontaneously broken. Since unbroken Z2 is a necessary condition for nonperturbative planar equivalence we conclude that the orbifold daughter is nonperturbatively nonequivalent to its supersymmetric parent. En route, our investigation reveals the existence of fractional domain walls, similar to fractional D-branes of string theory on orbifolds. We conjecture on the fate of these domain walls in the true solution of the Z2-broken orbifold theory. We also comment on relation with nonsupersymmetric string theories and closed-string tachyon condensation.Comment: 37 pages, 7 figures. v2: various significant changes; revisions explained in the introduction. Final version to appear in Phys.Rev.

    Anisotropic Electronic Structure of the Kondo Semiconductor CeFe2Al10 Studied by Optical Conductivity

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    We report temperature-dependent polarized optical conductivity [σ(ω)\sigma(\omega)] spectra of CeFe2_2Al10_{10}, which is a reference material for CeRu2_2Al10_{10} and CeOs2_2Al10_{10} with an anomalous magnetic transition at 28 K. The σ(ω)\sigma(\omega) spectrum along the b-axis differs greatly from that in the acac-plane, indicating that this material has an anisotropic electronic structure. At low temperatures, in all axes, a shoulder structure due to the optical transition across the hybridization gap between the conduction band and the localized 4f4f states, namely cc-ff hybridization, appears at 55 meV. However, the gap opening temperature and the temperature of appearance of the quasiparticle Drude weight are strongly anisotropic indicating the anisotropic Kondo temperature. The strong anisotropic nature in both electronic structure and Kondo temperature is considered to be relevant the anomalous magnetic phase transition in CeRu2_2Al10_{10} and CeOs2_2Al10_{10}.Comment: 5 pages, 4 figure

    Nonet meson properties in Nambu--Jona-Lasinio model with dimensional versus cutoff regularization

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    Nambu--Jona-Lasinio (NJL) model with Kobayashi-Maskawa-'t Hooft (KMT) term is one of low energy effective theory of QCD which includes the UA(1)U_A(1) anomaly. We investigate nonet meson properties in this model with three flavors of quarks. We employ two type of regularizations the dimensional and sharp cutoff ones. The model parameters are fixed phenomenologically for each regularization. Evaluating the kaon decay constant, the η\eta meson mass and the topological susceptibility, we show the regularization dependence of the results and discuss the applicability of the NJL model.Comment: 11 pages, 9 figure

    Uniaxial pressure dependencies of the phase transitions in GdMnO3_3

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    GdMnO3_3 shows an incommensurate antiferromagnetic order below 42\simeq 42 K, transforms into a canted A-type antiferromagnet below 20\simeq 20 K, and for finite magnetic fields along the b axis ferroelectric order occurs below 12\simeq 12 K. From high-resolution thermal expansion measurements along all three principal axes, we determine the uniaxial pressure dependencies of the various transition temperatures and discuss their correlation to changes of the magnetic exchange couplings in RRMnO3_3 (R=La,...DyR = {\rm La, ... Dy}).Comment: 2 pages, 3 figures, submitted to JMMM (Proceedings of ICM'06, Kyoto