278 research outputs found
Non-perturbative renormalization of vector and axial vector currents in quenched QCD for a renormalization group improved gauge action
Renormalization constants of vector () and axial-vector () currents
are determined non-perturbatively in quenched QCD for an RG-improved gauge
action and a tadpole-improved clover quark action using the Schr\"odinger
functional method. Meson decay constants and show much better
scaling when and estimated for infinite physical volume are used
instead of -factors from tadpole-improved one-loop perturbation theory.Comment: Lattice2003(improve), 3 page
I=2 Pion Scattering Length and Phase Shift with Wilson Fermions
We present preliminary results of scattering length and phase shift for I=2
S-wave system with the Wilson fermions in the quenched approximation.
The finite size method presented by L\"uscher is employed, and calculations are
carried out at on a and lattice.Comment: Lattice2001(spectrum
Dynamical fermions on anisotropic lattices
We report on our study of two-flavor full QCD on anisotropic lattices using
-improved Wilson quarks coupled with an RG-improved glue. The bare gauge
and quark anisotropies corresponding to the renormalized anisotropy
are determined as functions of and , using
the Wilson loop and the meson dispersion relation at several lattice cutoffs
and quark masses.Comment: Lattice2002(improve), 3 pages, 3 figure
I=2 pion-pion scattering phase shift in the continuum limit calculated with two-flavor full QCD
We present a calculation of the scattering phase shift for the I=2 S-wave
pion-pion system in the continuum limit with two-flavor full QCD. Calculations
are made at three lattice spacings, using the finite volume method of L\"uscher
in the center of mass frame, and its extension to the laboratory frame.Comment: Lattice2003(spectrum), 3 page
I=2 Pion Scattering Phase Shift with Wilson Fermions
We present a lattice QCD calculation of the scattering phase shift for the
I=2 -wave two-pion system using the finite size method proposed by
L\"uscher. We work in the quenched approximation employing the standard
plaquette action at for gluons and the Wilson fermion action for
quarks. The phase shift is extracted from the energy eigenvalues of the
two-pion system, which are obtained by a diagonalization of the pion 4-point
function evaluated for a set of relative spatial momenta. In order to change
momentum of the two-pion system, calculations are carried out on , , and lattices. The phase shift is
successfully calculated over the momentum range .Comment: LaTeX, 28 pages, 10 eps figures, uses revtex and epsfi
Protein Evolution within a Structural Space
Understanding of the evolutionary origins of protein structures represents a
key component of the understanding of molecular evolution as a whole. Here we
seek to elucidate how the features of an underlying protein structural "space"
might impact protein structural evolution. We approach this question using
lattice polymers as a completely characterized model of this space. We develop
a measure of structural comparison of lattice structures that is analgous to
the one used to understand structural similarities between real proteins. We
use this measure of structural relatedness to create a graph of lattice
structures and compare this graph (in which nodes are lattice structures and
edges are defined using structural similarity) to the graph obtained for real
protein structures. We find that the graph obtained from all compact lattice
structures exhibits a distribution of structural neighbors per node consistent
with a random graph. We also find that subgraphs of 3500 nodes chosen either at
random or according to physical constraints also represent random graphs. We
develop a divergent evolution model based on the lattice space which produces
graphs that, within certain parameter regimes, recapitulate the scale-free
behavior observed in similar graphs of real protein structures.Comment: 27 pages, 7 figure
Exploring QCD at small sea quark masses with improved Wilson-type quarks
We explore the region of small sea quark masses below in
two-flavor QCD using a mean-field improved clover quark action and an
RG-improved gauge action at fm on and lattices. We find that instability of the standard BiCGStab
algorithm at small quark masses can be mostly removed by the BiCGStab(DS-)
algorithm, which employs -th minimal residual polynomials with a dynamical
selection of . We also find singular spikes of in the HMC
algorithm at moderate values of . Nature of the spike is studied.
We also study finite-size effects and chiral properties of meson masses.Comment: 3 pages, 4 figures, Lattice2002(spectrum
Moral emotions and justifying beliefs about meat, fish, dairy and egg consumption: A comparative study of dietary groups
YesMeat eaters and meat abstainers differ in their beliefs and moral emotions related to meat consumption alongside gender differences. Few studies have investigated beliefs and moral emotions in pescatarians and vegans. Little is known about differences in moral emotions and beliefs regarding dairy, eggs, and fish or about speciesist beliefs within and between specific dietary groups. To address this gap, we investigated moral emotions (consumption-related disgust and guilt), attitudes towards animals (Animal Attitudes Scale) and justifying beliefs related to meat (Carnism Inventory), dairy, egg, and fish consumption in omnivores (n = 167), pescatarians (n = 110), vegetarians (n = 116), and vegans (n = 149). Results showed that people who consumed animal-derived products reported lower disgust and guilt and held stronger justifying beliefs about consumption of these products, than those who did not consume animal products. All dietary groups significantly differed from each other in their attitudes about using animals for human benefit, with omnivores showing the least positive attitudes towards animals, followed by pescatarians and vegetarians, and with vegans showing the most positive attitudes towards animals. Women experienced greater moral emotions and held fewer justifying beliefs than men within groups where animal products were consumed and this was related to the animal-based products they consume (i.e., fish for pescatarians and eggs/dairy for vegetarians). These findings emphasise the importance of considering a wider range of animal products, and dietary groups in order to obtain a comprehensive understanding of the psychological underpinnings of animal product consumption. The results highlight differences between dietary groups in attitudes and moral concern towards animals, which may be important to consider when designing interventions to reduce animal product consumption
Light hadron spectroscopy in two-flavor QCD with small sea quark masses
We extend the study of the light hadron spectrum and the quark mass in
two-flavor QCD to smaller sea quark mass, corresponding to
--0.35. Numerical simulations are carried out using the
RG-improved gauge action and the meanfield-improved clover quark action at
( fm from meson mass). We observe that the light
hadron spectrum for small sea quark mass does not follow the expectation from
chiral extrapolations with quadratic functions made from the region of
--0.55. Whereas fits with either polynomial or continuum
chiral perturbation theory (ChPT) fails, the Wilson ChPT (WChPT) that includes
effects associated with explicit chiral symmetry breaking successfully
fits the whole data: In particular, WChPT correctly predicts the light quark
mass spectrum from simulations for medium heavy quark mass, such as m_{PS}/m_V
\simgt 0.5. Reanalyzing the previous data %at --0.55 with
the use of WChPT, we find the mean up and down quark mass being smaller than
the previous result from quadratic chiral extrapolation by approximately 10%,
[MeV] in the continuum limit.Comment: 33 page
- …