95,493 research outputs found
Light Hadron Spectroscopy on Coarse Lattices with O(a^2) Mean-Field Improved Actions
The masses and dispersions of light hadrons are calculated in lattice QCD
using an O(a^2) tadpole-improved gluon action and an O(a^2) tadpole-improved
next-nearest-neighbor fermion action originally proposed by Hamber and Wu. Two
lattices of constant volume with lattice spacings of approximately 0.40 fm and
0.24 fm are considered. The results reveal some scaling violations at the
coarser lattice spacing on the order of 5%. At the finer lattice spacing, the
calculated mass ratios reproduce state-of-the-art results using unimproved
actions. Good dispersion and rotational invariance up to momenta of pa ~ 1 are
also found. The relative merit of alternative choices for improvement operators
is assessed through close comparisons with other plaquette-based
tadpole-improved actions.Comment: 17 page RevTeX manuscript. 7 Figures. This and related papers may
also be obtained from
http://www.physics.adelaide.edu.au/~dleinweb/Publications.htm
Time Quantified Monte Carlo Algorithm for Interacting Spin Array Micromagnetic Dynamics
In this paper, we reexamine the validity of using time quantified Monte Carlo
(TQMC) method [Phys. Rev. Lett. 84, 163 (2000); Phys. Rev. Lett. 96, 067208
(2006)] in simulating the stochastic dynamics of interacting magnetic
nanoparticles. The Fokker-Planck coefficients corresponding to both TQMC and
Langevin dynamical equation (Landau-Lifshitz-Gilbert, LLG) are derived and
compared in the presence of interparticle interactions. The time quantification
factor is obtained and justified. Numerical verification is shown by using TQMC
and Langevin methods in analyzing spin-wave dispersion in a linear array of
magnetic nanoparticles.Comment: Accepted for publication in Phys. Rev.
Solving the Master Equation for Extremely Long Time Scale Calculations
The dynamics of magnetic reversal process plays an important role in the
design of the magnetic recording devices in the long time scale limit. In
addition to long time scale, microscopic effects such as the entropic effect
become important in magnetic nano-scale systems. Many advanced simulation
methods have been developed, but few have the ability to simulate the long time
scale limit and to accurately model the microscopic effects of nano-scale
systems at the same time. We develop a new Monte Carlo method for calculating
the dynamics of magnetic reversal at arbitrary long time. For example, actual
calculations were performed up to 1e50 Monte Carlo steps. This method is based
on microscopic interactions of many constituents and the master equation for
magnetic probability distribution function is solved symbolically.Comment: accepted for publication in Computer Physics and Communication
Cold electron beams from cryo-cooled, alkali antimonide photocathodes
In this letter we report on the generation of cold electron beams using a
Cs3Sb photocathode grown by co-deposition of Sb and Cs. By cooling the
photocathode to 90 K we demonstrate a significant reduction in the mean
transverse energy validating the long standing speculation that the lattice
temperature contribution limits the mean transverse energy or thermal emittance
near the photoemission threshold, opening new frontiers in generating
ultra-bright beams. At 90 K, we achieve a record low thermal emittance of 0.2
m (rms) per mm of laser spot diameter from an ultrafast (sub-picosecond)
photocathode with quantum efficiency greater than using a
visible laser wavelength of 690 nm
A metal–organic framework/α-alumina composite with a novel geometry for enhanced adsorptive separation
The development of a metal–organic framework/α-alumina composite leads to a novel concept: efficient adsorption occurs within a plurality of radial micro-channels with no loss of the active adsorbents during the process. This composite can effectively remediate arsenic contaminated water producing potable water recovery, whereas the conventional fixed bed requires eight times the amount of active adsorbents to achieve a similar performance
Pion Decay Constant, and Chiral Log from Overlap Fermions
We report our calculation of the pion decay constant , the axial
renormalization constant , and the quenched chiral logarithms from the
overlap fermions. The calculation is done on a quenched lattice at
fm using tree level tadpole improved gauge action. The smallest pion
mass we reach is about 280 MeV. The lattice size is about 4 times the Compton
wavelength of the lowest mass pion.Comment: Lattice2001(Hadronic Matrix Elements), 3pages, 5figure
Analytical Solution to Transport in Brownian Ratchets via Gambler's Ruin Model
We present an analogy between the classic Gambler's Ruin problem and the
thermally-activated dynamics in periodic Brownian ratchets. By considering each
periodic unit of the ratchet as a site chain, we calculated the transition
probabilities and mean first passage time for transitions between energy minima
of adjacent units. We consider the specific case of Brownian ratchets driven by
Markov dichotomous noise. The explicit solution for the current is derived for
any arbitrary temperature, and is verified numerically by Langevin simulations.
The conditions for vanishing current and current reversal in the ratchet are
obtained and discussed.Comment: 4 pages, 3 figure
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