36,377 research outputs found

    The intruder feature of 31Mg and the coexistence of many particle and many hole states

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    The low-lying level structure of 31Mg^{31}{\rm Mg} has been investigated by the antisymmetrized molecular dynamics (AMD) plus generator coordinate method (GCM) with the Gogny D1S force. It is shown that the N=20 magic number is broken and the ground state has the pure neutron 2p3h2p3h configuration. The coexistence of many particle and many hole states at very low excitation energy is discussed

    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

    Stochastic delocalization of finite populations

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    Heterogeneities in environmental conditions often induce corresponding heterogeneities in the distribution of species. In the extreme case of a localized patch of increased growth rates, reproducing populations can become strongly concentrated at the patch despite the entropic tendency for population to distribute evenly. Several deterministic mathematical models have been used to characterize the conditions under which localized states can form, and how they break down due to convective driving forces. Here, we study the delocalization of a finite population in the presence of number fluctuations. We find that any finite population delocalizes on sufficiently long time scales. Depending on parameters, however, populations may remain localized for a very long time. The typical waiting time to delocalization increases exponentially with both population size and distance to the critical wind speed of the deterministic approximation. We augment these simulation results by a mathematical analysis that treats the reproduction and migration of individuals as branching random walks subject to global constraints. For a particular constraint, different from a fixed population size constraint, this model yields a solvable first moment equation. We find that this solvable model approximates very well the fixed population size model for large populations, but starts to deviate as population sizes are small. The analytical approach allows us to map out a phase diagram of the order parameter as a function of the two driving parameters, inverse population size and wind speed. Our results may be used to extend the analysis of delocalization transitions to different settings, such as the viral quasi-species scenario

    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