30,177 research outputs found
Schroedinger functional formalism with domain-wall fermion
Finite volume renormalization scheme is one of the most fascinating scheme
for non-perturbative renormalization on lattice.
By using the step scaling function one can follow running of renormalized
quantities with reasonable cost.
It has been established the Schroedinger functional is very convenient to
define a field theory in a finite volume for the renormalization scheme.
The Schroedinger functional, which is characterized by a
Dirichlet boundary condition in temporal direction, is well defined and works
well for the Yang-Mills theory and QCD with the Wilson fermion.
However one easily runs into difficulties if one sets the same sort of the
Dirichlet boundary condition for the overlap Dirac operator or the domain-wall
fermion.
In this paper we propose an orbifolding projection procedure to impose the
Schroedinger functional Dirichlet boundary condition on the domain-wall
fermion.Comment: 32 page
Photoinjector-generation of a flat electron beam with transverse emittance ratio of 100
The generation of a flat electron beam directly from a photoinjector is an
attractive alternative to the electron damping ring as envisioned for linear
colliders. It also has potential applications to light sources such as the
generation of ultra-short x-ray pulses or Smith-Purcell free electron lasers.
In this Letter, we report on the experimental generation of a flat-beam with a
measured transverse emittance ratio of for a bunch charge of
nC; the smaller measured normalized root-mean-square emittance is
m and is limited by the resolution of our experimental setup.
The experimental data, obtained at the Fermilab/NICADD Photoinjector
Laboratory, are compared with numerical simulations and the expected scaling
laws.Comment: 5 pages, 3 figure
Signal enhancement of the in-plane and out-of-plane Rayleigh wave components
Several groups have reported an enhancement of the ultrasonic Rayleigh wave when scanning close to a surface-breaking defect in a metal sample. This enhancement may be explained as an interference effect where the waves passing directly between source and receiver interfere with those waves reflected back from the defect. We present finite element models of the predicted enhancement when approaching a defect, along with experiments performed using electromagnetic acoustic transducers sensitive to either in-plane or out-of-plane motion. A larger enhancement of the in-plane motion than the out-of-plane motion is observed and can be explained by considering ultrasonic reflections and mode conversion at the defect
Domain Wall Fermions with Exact Chiral Symmetry
We show how the standard domain wall action can be simply modified to allow
arbitrarily exact chiral symmetry at finite fifth dimensional extent. We note
that the method can be used for both quenched and dynamical calculations. We
test the method using smooth and thermalized gauge field configurations. We
also make comparisons of the performance (cost) of the domain wall operator for
spectroscopy compared to other methods such as the overlap-Dirac operator and
find both methods are comparable in cost.Comment: revtex, 37 pages, 11 color postscript figure
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Preferential localization of a vesicular monoamine transporter to dense core vesicles in PC12 cells.
Neurons and endocrine cells have two types of secretory vesicle that undergo regulated exocytosis. Large dense core vesicles (LDCVs) store neural peptides whereas small clear synaptic vesicles store classical neurotransmitters such as acetylcholine, gamma-aminobutyric acid (GABA), glycine, and glutamate. However, monoamines differ from other classical transmitters and have been reported to appear in both LDCVs and smaller vesicles. To localize the transporter that packages monoamines into secretory vesicles, we have raised antibodies to a COOH-terminal sequence from the vesicular amine transporter expressed in the adrenal gland (VMAT1). Like synaptic vesicle proteins, the transporter occurs in endosomes of transfected CHO cells, accounting for the observed vesicular transport activity. In rat pheochromocytoma PC12 cells, the transporter occurs principally in LDCVs by both immunofluorescence and density gradient centrifugation. Synaptic-like microvesicles in PC12 cells contain relatively little VMAT1. The results appear to account for the storage of monoamines by LDCVs in the adrenal medulla and indicate that VMAT1 provides a novel membrane protein marker unique to LDCVs
Are Topological Charge Fluctuations in QCD Instanton Dominated?
We consider a recent proposal by Horv\'ath {\em et al.} to address the
question whether topological charge fluctuations in QCD are instanton dominated
via the response of fermions using lattice fermions with exact chiral symmetry,
the overlap fermions. Considering several volumes and lattice spacings we find
strong evidence for chirality of a finite density of low-lying eigenvectors of
the overlap-Dirac operator in the regions where these modes are peaked. This
result suggests instanton dominance of topological charge fluctuations in
quenched QCD.Comment: LaTeX, 15 pages, 8 postscript figures, minor improvements, version to
appear in PR
Non-linear enhancement of laser generated ultrasonic Rayleigh waves by cracks
Laser generated ultrasound has been widely used for detecting cracks, surface and sub-surface defects in
many different materials. It provides a non-contact wideband excitation source which can be focused into
different geometries. Previous workers have reported enhancement of the laser generated Rayleigh wave
when a crack is illuminated by pulsed laser beam irradiation. We demonstrate that the enhancement
observed is due to a combination of source truncation, the free boundary condition at the edge of the crack
and interference effects. Generating a Rayleigh wave over a crack can lead to enhancement of the
amplitude of the Rayleigh wave signal, a shift in the dominant frequency of the wideband Rayleigh wave
and strong enhancement of the high frequency components of the Rayleigh wave
The quantum-mechanical basis of an extended Landau-Lifshitz-Gilbert equation for a current-carrying ferromagnetic wire
An extended Landau-Lifshitz-Gilbert (LLG) equation is introduced to describe
the dynamics of inhomogeneous magnetization in a current-carrying wire. The
coefficients of all the terms in this equation are calculated
quantum-mechanically for a simple model which includes impurity scattering.
This is done by comparing the energies and lifetimes of a spin wave calculated
from the LLG equation and from the explicit model. Two terms are of particular
importance since they describe non-adiabatic spin-transfer torque and damping
processes which do not rely on spin-orbit coupling. It is shown that these
terms may have a significant influence on the velocity of a current-driven
domain wall and they become dominant in the case of a narrow wall.Comment: 19 pages, 1 figur
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