21,587 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
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
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
Explicit solutions of the classical Calogero & Sutherland systems for any root system
Explicit solutions of the classical Calogero (rational with/without harmonic
confining potential) and Sutherland (trigonometric potential) systems is
obtained by diagonalisation of certain matrices of simple time evolution. The
method works for Calogero & Sutherland systems based on any root system. It
generalises the well-known results by Olshanetsky and Perelomov for the A type
root systems. Explicit solutions of the (rational and trigonometric) higher
Hamiltonian flows of the integrable hierarchy can be readily obtained in a
similar way for those based on the classical root systems.Comment: 18 pages, LaTeX, no figur
Fractional Flux Periodicity in Doped Carbon Nanotubes
An anomalous magnetic flux periodicity of the ground state is predicted in
two-dimensional cylindrical surface composed of square and honeycomb lattice.
The ground state and persistent currents exhibit an approximate fractional
period of the flux quantum for a specific Fermi energy. The period depends on
the aspect ratio of the cylinder and on the lattice structure around the axis.
We discuss possibility of this nontrivial periodicity in a heavily doped
armchair carbon nanotube.Comment: 5 pages, 4 figure
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