8,249 research outputs found
B meson light-cone wavefunctions in the heavy quark limit
We present a systematic study of the B meson light-cone wavefunctions in QCD
in the heavy-quark limit. We construct model-independent formulae for the
light-cone wavefunctions in terms of independent dynamical degrees of freedom,
which exactly satisfy the QCD equations of motion and constraints from
heavy-quark symmetry. The results demonstrate novel behaviors of longitudinal
as well as transverse momentum distribution in the B mesons.Comment: 5 pages LaTeX, 1 style file. Talk presented at RADCOR/Loops and Legs
2002, Kloster Banz, Germany, September 8-13, 200
Dynamical simulation of spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin glasses
Spin-glass and chiral-glass orderings in three-dimensional Heisenberg spin
glasses are studied with and without randaom magnetic anisotropy by dynamical
Monte Carlo simulations. In isotropic case, clear evidence of a
finite-temperature chiral-glass transition is presented. While the spin
autocorrelation exhibits only an interrupted aging, the chirality
autocorrelation persists to exhibit a pronounced aging effect reminisecnt of
the one observed in the mean-field model. In anisotropic case, asymptotic
mixing of the spin and the chirality is observed in the off-equilibrium
dynamics.Comment: 4 pages including 5 figures, LaTex, to appear in Phys. Rev. Let
Ordering of the Heisenberg Spin Glass in High Dimensions
Ordering of the Heisenberg spin glass with the nearest-neighbor Gaussian
coupling is investigated by equilibrium Monte Carlo simulations in four and
five dimensions. Ordering of the mean-field Heisenberg spin-glass is also
studied for comparison. Particular attention is paid to the nature of the
spin-glass and the chiral-glass orderings. Our numerical data suggest that, in
five dimensions, the model exhibits a single spin-glass transition at a finite
temperature, where the spin-glass order accompanying the simultaneous
chiral-glass order sets in. In four dimensions, by contrast, the model exhibits
a chiral-glass transition at a finite temperature, not accompanying the
standard spin-glass order. The critical region associated with the chiral-glass
transition, however, is very narrow, suggesting that dimension four is close to
the marginal dimensionality.Comment: 18 pages, 12 figure
Ordering of the Heisenberg spin glass in two dimensions
The spin and the chirality orderings of the Heisenberg spin glass in two
dimensions with the nearest-neighbor Gaussian coupling are investigated by
equilibrium Monte Carlo simulations. Particular attention is paid to the
behavior of the spin and the chirality correlation lengths. In order to observe
the true asymptotic behavior, fairly large system size L\gsim 20 (L the linear
dimension of the system) appears to be necessary. It is found that both the
spin and the chirality order only at zero temperature. At high temperatures,
the chiral correlation length stays shorter than spin correlation length,
whereas at lower temperatures below the crossover temperature T_\times, the
chiral correlation length exceeds the spin correlation length. The spin and the
chirality correlation-length exponents are estimated above T_\times to be
\nu_SG=0.9+-0.2 and \nu_CG=2.1+-0.3, respectively. These values are close to
the previous estimates on the basis of the domain-wall-energy calculation.
Discussion is given about the asymptotic critical behavior realized below
T_\times.Comment: to appear in a special issue of J. Phys.
Monte Carlo Studies of the Ordering of the Three-Dimensional Isotropic Heisenberg Spin Glass in Magnetic Fields
Spin and chirality orderings of the three-dimensional Heisenberg spin glass
under magnetic fields are studied by large-scale equilibrium Monte Carlo
simulations. It is found that the chiral-glass transition and the chiral-glass
ordered state, which are essentially of the same character as their zero-field
counterparts, occur under magnetic fields. The chiral-glass ordered state
exhibits a one-step-like peculiar replica-symmetry breaking in the chiral
sector, while it does not accompany the spin-glass order perpendicular to the
applied field. Critical perperties of the chiral-glass transition are different
from those of the standard Ising spin glass. Magnetic phase diagram of the
model is constructed, which reveals that the chiral-glass state is quite robust
against magnetic fields. The chiral-glass transition line has a character of
the Gabay-Toulouse line of the mean-field model, yet its physical origin being
entirely different. These numerical results are discussed in light of the
recently developed spin-chirality decoupling-recoupling scenario. Implication
to experimental phase diagram is also discussed.Comment: 23 pages, 23 figure
Nature of the vortex-glass order in strongly type-II superconductors
The stability and the critical properties of the three-dimensional
vortex-glass order in random type-II superconductors with point disorder is
investigated in the unscreened limit based on a lattice {\it XY} model with a
uniform field. By performing equilibrium Monte Carlo simulations for the system
with periodic boundary conditions, the existence of a stable vortex-glass order
is established in the unscreened limit. Estimated critical exponents are
compared with those of the gauge-glass model.Comment: Error in the reported value of the exponent eta is correcte
Spin and chirality orderings of the one-dimensional Heisenberg spin glass with the long-range power-law interaction
The ordering of the one-dimensional Heisenberg spin glass interacting via the
long-range power-law interaction is studied by Monte Carlo simulations.
Particular attention is paid to the possible occurrence of the ``spin-chirality
decoupling'' for appropriate values of the power-law exponent \sigma. Our
result suggests that, for intermediate values of , the chiral-glass
order occurs at finite temperatures while the standard spin-glass order occurs
only at zero temperature.Comment: Proceedings of the Highly Frustrated Magnetism (HFM2006) conference.
To appear in a special issue of J. Phys. Condens. Matte
Dynamical Critical Phenomena in three-dimensional Heisenberg Spin Glasses
Spin-glass (SG) and chiral-glass (CG) orderings in three dimensional (3D)
Heisenberg spin glass with and without magnetic anisotropy are studied by using
large-scale off-equilibrium Monte Carlo simulations. A characteristic time of
relaxation, which diverges at a transition temperature in the thermodynamic
limit, is obtained as a function of the temperature and the system size. Based
on the finite-size scaling analysis for the relaxation time, it is found that
in the isotropic Heisenberg spin glass, the CG phase transition occurs at a
finite temperature, while the SG transition occurs at a lower temperature,
which is compatible with zero. Our results of the anisotropic case support the
chirality scenario for the phase transitions in the 3D Heisenberg spin glasses.Comment: 9 pages, 19 figure
First-Order Transition to Incommensurate Phase with Broken Lattice Rotation Symmetry in Frustrated Heisenberg Model
We study a finite-temperature phase transition in the two-dimensional
classical Heisenberg model on a triangular lattice with a ferromagnetic
nearest-neighbor interaction and an antiferromagnetic
third-nearest-neighbor interaction using a Monte Carlo method. Apart from
a trivial degeneracy corresponding to O(3) spin rotations,the ground state for
has a threefold degeneracy corresponding to 120 degree lattice
rotations. We find that this model exhibits a first-order phase transition with
the breaking of the threefold symmetry when the interaction ratio is
.Comment: 4pages,5figure
A comparison between the catching efficiency of two milkfish fry collecting gears and their respective modifications
An experiment was conducted along the shore of Culasi, Antique in Panay to compare the milkfry (Chanos chanos) catching efficiency of the ordinary fry seine against its innovation and the ordinary sweeper against its 2 modifications. Results show that it is possible to replace the wings of the presently used sweeper and the ends of the fry seine with a coarse-meshed netting. This improvement decreases the water resistance of the gears and thus enables fry gatherers to use larger ones thereby giving more catch
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