25,386 research outputs found

    Excited nucleon spectrum from lattice QCD with maximum entropy method

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    We study excited states of the nucleon in quenched lattice QCD with the spectral analysis using the maximum entropy method. Our simulations are performed on three lattice sizes 163×3216^3\times 32, 243×3224^3\times 32 and 323×3232^3\times 32, at β=6.0\beta=6.0 to address the finite volume issue. We find a significant finite volume effect on the mass of the Roper resonance for light quark masses. After removing this systematic error, its mass becomes considerably reduced toward the direction to solve the level order puzzle between the Roper resonance N(1440)N'(1440) and the negative-parity nucleon N(1535)N^*(1535).Comment: Lattice2003(spectrum), 3 pages, 4 figure

    Pseudospin and Deformation-induced Gauge Field in Graphene

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    The basic properties of π\pi-electrons near the Fermi level in graphene are reviewed from a point of view of the pseudospin and a gauge field coupling to the pseudospin. The applications of the gauge field to the electron-phonon interaction and to the edge states are reported.Comment: 27 pages, 7 figure

    Polarization Dependence of Raman Spectra in Strained Graphene

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    The polarization dependences of the G, D, and 2D (G') bands in Raman spectra at graphene bulk and edge are examined theoretically. The 2D and D bands have different selection rules at bulk and edge. At bulk, the 2D band intensity is maximum when the polarization of the scattered light is parallel to that of incident light, whereas the D band intensity does not have a polarization dependence. At edge, the 2D and D bands exhibit a selection rule similar to that of the G band proposed in a previous paper. We suggest that a constraint equation on the axial velocity caused by the graphene edge is essential for the dependence of the G band on the crystallographic orientation observed in the bulk of strained graphene. This is indicative of that the pseudospin and valleyspin in the bulk of graphene can not be completely free from the effect of surrounding edge. The status of the experiments on the G and D bands at the graphene edge is mentioned.Comment: 11 pages, 3 figure

    Bayesian approach to the first excited nucleon state in lattice QCD

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    We present preliminary results from the first attempt to reconstruct the spectral function in the nucleon and Δ\Delta channels from lattice QCD data using the maximum entropy method (MEM). An advantage of the MEM analysis is to enable us to access information of the excited state spectrum. Performing simulations on two lattice volumes, we confirm the large finite size effect on the first excited nucleon state in the lighter quark mass region.Comment: Lattice2002(spectrum), Latex with espcrc2.sty, 3 pages, 3 figure

    Effect of surface roughness on friction behaviour of steel under boundary lubrication

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    The friction behaviour of grinded and polished surfaces was evaluated by using a reciprocal sliding tester under lubrication with PAO, PAO + ZnDTP and PAO + ZnDTP + MoDTC. Friction coefficients on the smooth surfaces showed higher values compared to those on the rough surfaces. For lubrication incorporating PAO and PAO + ZnDTP + MoDTC, friction coefficients on both the smoothest and the roughest surfaces decreased with sliding time. On the other hand, friction coefficients between these extremes decreased with sliding time. In this paper, the effects of surface roughness on friction behaviour are discussed

    Gap Condition and Self-Dualized N=4{\cal N}=4 Super Yang-Mills Theory for ADE Gauge Group on K3

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    We try to determine the partition function of N=4{\cal N}=4 super Yang-Mills theoy for ADE gauge group on K3 by self-dualizing our previous ADE partition function. The resulting partition function satisfies gap condition.Comment: 17 page

    Aharanov-Bohm effect for the edge states of zigzag carbon nanotubes

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    Two delocalized states of metallic zigzag carbon nanotubes near the Dirac point can be localized by the Aharanov-Bohm magnetic field around 20 Tesla. The dependence of the localization on the length and diameter of the nanotubes shows that the localization-delocalization transition can be observed for 2 nm diameter tube. The mechanism of the localization is explained in terms of the deformation-induced gauge field, which shows a topological nature of the localization. The transition from the delocalized states to the localized states can be observed by scanning tunneling microscopy and spectroscopy. A similarity between the transition and the spin Hall effect is discussed.Comment: 7 pages, 4 figure

    Susceptibilities and the Phase Structure of a Chiral Model with Polyakov Loops

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    In an extension of the Nambu-Jona-Lasinio model where the quarks interact with the temporal gluon field, represented by the Polyakov loop, we explore the relation between the deconfinement and chiral phase transitions. The effect of Polyakov loop dynamics on thermodynamic quantities, on the phase structure at finite temperature and baryon density and on various susceptibilities is presented. Particular emphasis is put on the behavior and properties of the fluctuations of the (approximate) order parameters and their dependence on temperature and net--quark number density. We also discuss how the phase structure of the model is influenced by the coupling of the quarks to the Polyakov loop.Comment: 18 pages, 22 figures; text rearranged and references added. results and conclusions unchanged; final version accepted for publication in Phys. Rev.
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