35,065 research outputs found
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
Universal Scaling of the Chiral Condensate in Finite-Volume Gauge Theories
We confront exact analytical predictions for the finite-volume scaling of the
chiral condensate with data from quenched lattice gauge theory simulations.
Using staggered fermions in both the fundamental and adjoint representations,
and gauge groups SU(2) and SU(3), we are able to test simultaneously all of the
three chiral universality classes. With overlap fermions we also test the
predictions for gauge field sectors of non-zero topological charge. Excellent
agreement is found in most cases, and the deviations are understood in the
others.Comment: Expanded discussion of overlap fermion results. 17 pages revtex, 7
postscript figure
Finite-Volume Scaling of the Quenched Chiral Condensate
In the large-volume limit with the
mass-dependent chiral condensate is predicted to satisfy exact finite-volume
scaling laws that fall into three major universality classes. We test these
analytical predictions with staggered fermions and overlap fermions in gauge
field sectors of fixed topological charge .Comment: Talk at Lattice99(topology), 3 page
The impact of Chinese import penetration on the South African manufacturing sector
This article uses a Chenery-type decomposition and econometric estimation to evaluate the impact of Chinese trade on production and employment in South African manufacturing from 1992 to 2010. The results suggest that increased import penetration from China caused South African manufacturing output to be 5 per cent lower in 2010 than it otherwise would have been. The estimated reduction of total employment in manufacturing as a result of trade with China is larger – in 2010 about 8 per cent – because the declines in output were concentrated on labour-intensive industries and because the increase in imports raised labour productivity within industries
An alternative to domain wall fermions
We define a sparse hermitian lattice Dirac matrix, , coupling Dirac
fermions. When fermions are integrated out the induced action for the last
fermion is a rational approximation to the hermitian overlap Dirac operator. We
provide rigorous bounds on the condition number of and compare them to
bounds for the higher dimensional Dirac operator of domain wall fermions. Our
main conclusion is that overlap fermions should be taken seriously as a
practical alternative to domain wall fermions in the context of numerical QCD.Comment: Revtex Latex, 26 pages, 1 figure, a few minor change
Generalised Spin Projection for Fermion Actions
The majority of compute time doing lattice QCD is spent inverting the fermion
matrix. The time that this takes increases with the condition number of the
matrix. The FLIC(Fat Link Irrelevant Clover) action displays, among other
properties, an improved condition number compared to standard actions and hence
is of interest due to potential compute time savings. However, due to its two
different link sets there is a factor of two cost in floating point
multiplications compared to the Wilson action. An additional factor of two has
been attributed due to the loss of the so-called spin projection trick. We show
that any split-link action may be written in terms of spin projectors, reducing
the additional cost to at most a factor of two. Also, we review an efficient
means of evaluating the clover term, which is additional expense not present in
the Wilson action.Comment: 4 page
Parsec Scale Properties of Markarian 501
We present the results of a high angular resolution study of the BL Lac
object Markarian 501 in the radio band. We consider data taken at 14 different
epochs, ranging between 1.6 GHz and 22 GHz in frequency, and including new
Space VLBI observations obtained on 2001 March 5 and 6 at 1.6 and 5 GHz. We
study the kinematics of the parsec-scale jet and estimate its bulk velocity and
orientation with respect to the line of sight. Limb brightened structure in the
jet is clearly visible in our data and we discuss its possible origin in terms
of velocity gradients in the jet. Quasi-simultaneous multi-wavelength
observations allow us to map the spectral index distribution and to compare it
to the jet morphology. Finally, we estimate the physical parameters of the
parsec-scale jet.Comment: accepted for publication in ApJ; 24 pages with 17 figures (fig. 1 and
fig. 2 available only as .jpg files
Comment on Path Integral Derivation of Schr\"odinger Equation in Spaces with Curvature and Torsion
We present a derivation of the Schr\"odinger equation for a path integral of
a point particle in a space with curvature and torsion which is considerably
shorter and more elegant than what is commonly found in the literature.Comment: LaTeX file in sr
Interacting Bose and Fermi gases in low dimensions and the Riemann hypothesis
We apply the S-matrix based finite temperature formalism to non-relativistic
Bose and Fermi gases in 1+1 and 2+1 dimensions. In the 2+1 dimensional case,
the free energy is given in terms of Roger's dilogarithm in a way analagous to
the relativistic 1+1 dimensional case. The 1d fermionic case with a
quasi-periodic 2-body potential provides a physical framework for understanding
the Riemann hypothesis.Comment: version 3: additional appendix explains how the to
duality of Riemann's follows from a special modular
transformation in a massless relativistic theor
- …