25,672 research outputs found
Excited nucleon spectrum from lattice QCD with maximum entropy method
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 , and
, at 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 and the negative-parity nucleon
.Comment: Lattice2003(spectrum), 3 pages, 4 figure
Pseudospin and Deformation-induced Gauge Field in Graphene
The basic properties of -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
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
We present preliminary results from the first attempt to reconstruct the
spectral function in the nucleon and 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
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 Super Yang-Mills Theory for ADE Gauge Group on K3
We try to determine the partition function of 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
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
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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