184 research outputs found
Dynamical QCD thermodynamics with domain wall fermions
We present results from numerical simulations of full, two flavor QCD
thermodynamics at N_t=4 with domain wall fermions. For the first time a
numerical simulation of the full QCD phase transition displays a low
temperature phase with spontaneous chiral symmetry breaking but intact flavor
symmetry and a high temperature phase with the full SU(2) x SU(2) chiral flavor
symmetry.Comment: LATTICE98(hightemp
Quenched QCD with domain wall fermions
We report on simulations of quenched QCD using domain wall fermions, where we
focus on basic questions about the formalism and its ability to produce
expected low energy hadronic physics for light quarks. The work reported here
is on quenched lattices at and 5.85, using values
for the length of the fifth dimension between 10 and 48. We report results for
parameter choices which lead to the desired number of flavors, a study of
undamped modes in the extra dimension and hadron masses.Comment: Contribution to Lattice '98. Presented by R. Mawhinney. 3 pages, 3
figure
The domain wall fermion chiral condensate in quenched QCD
We examine the chiral limit of domain wall fermions in quenched QCD. One
expects that in a quenched simulation, exact fermion zero modes will give a
divergent, 1/m behavior in the chiral condensate for sufficiently small valence
quark masses. Unlike other fermion formulations, domain wall fermions clearly
demonstrate this behavior.Comment: LATTICE98(spectrum), G. R. Fleming presented talk, 5 pages, 3
figures, corrected typos in printed versio
Studying the impact of ocean eddies on the ecosystem of the Prince Edward Islands: DEIMEC ll
The Dynamics of Eddy Impacts on Marion’s Ecosystem Study (DEIMEC) programme was begun in 2002 with the aim of understanding the importance of the oceanic, upstream environment to the ecosystem of the Prince Edward Islands. This island group consists of two small volcanic islands and provides many opportunities for studying ecological and evolutionary processes, for monitoring ecological changes in relation to global climate change and for conserving a unique component of the planet’s biological diversity
The finite temperature QCD phase transition with domain wall fermions
The domain wall formulation of lattice fermions is expected to support
accurate chiral symmetry, even at finite lattice spacing. Here we attempt to
use this new fermion formulation to simulate two-flavor, finite temperature QCD
near the chiral phase transition. In this initial study, a variety of quark
masses, domain wall heights and domain wall separations are explored using an
8^3 x 4 lattice. Both the expectation value of the Wilson line and the chiral
condensate show the temperature dependence expected for the QCD phase
transition. Further, the desired chiral properties are seen for the chiral
condensate, suggesting that the domain wall fermion formulation may be an
effective approach for the numerical study of QCD at finite temperature.Comment: 44 pages, 15 figure
Enemies with benefits: parasitic endoliths protect mussels against heat stress
Positive and negative aspects of species interactions can be context dependant and strongly affected by environmental conditions. We tested the hypothesis that, during periods of intense heat stress, parasitic phototrophic endoliths that fatally degrade mollusc shells can benefit their mussel hosts. Endolithic infestation significantly reduced body temperatures of sun-exposed mussels and, during unusually extreme heat stress, parasitised individuals suffered lower mortality rates than nonparasitised hosts. This beneficial effect was related to the white discolouration caused by the excavation activity of endoliths. Under climate warming, species relationships may be drastically realigned and conditional benefits of phototrophic endolithic parasites may become more important than the costs of infestation
Quenched Lattice QCD with Domain Wall Fermions and the Chiral Limit
Quenched QCD simulations on three volumes, , and
and three couplings, , 5.85 and 6.0 using domain
wall fermions provide a consistent picture of quenched QCD. We demonstrate that
the small induced effects of chiral symmetry breaking inherent in this
formulation can be described by a residual mass (\mres) whose size decreases
as the separation between the domain walls () is increased. However, at
stronger couplings much larger values of are required to achieve a given
physical value of \mres. For and , we find
\mres/m_s=0.033(3), while for , and ,
\mres/m_s=0.074(5), where is the strange quark mass. These values are
significantly smaller than those obtained from a more naive determination in
our earlier studies. Important effects of topological near zero modes which
should afflict an accurate quenched calculation are easily visible in both the
chiral condensate and the pion propagator. These effects can be controlled by
working at an appropriately large volume. A non-linear behavior of in
the limit of small quark mass suggests the presence of additional infrared
subtlety in the quenched approximation. Good scaling is seen both in masses and
in over our entire range, with inverse lattice spacing varying between
1 and 2 GeV.Comment: 91 pages, 34 figure
Domain wall fermion zero modes on classical topological backgrounds
The domain wall approach to lattice fermions employs an additional dimension,
in which gauge fields are merely replicated, to separate the chiral components
of a Dirac fermion. It is known that in the limit of infinite separation in
this new dimension, domain wall fermions have exact zero modes, even for gauge
fields which are not smooth. We explore the effects of finite extent in the
fifth dimension on the zero modes for both smooth and non-smooth topological
configurations and find that a fifth dimension of around ten sites is
sufficient to clearly show zero mode effects. This small value for the extent
of the fifth dimension indicates the practical utility of this technique for
numerical simulations of QCD.Comment: Updated fig. 3-7, small changes in sect. 3, added fig. 8, added more
reference
Super Yang-Mills on the lattice with domain wall fermions
The dynamical N=1, SU(2) Super Yang-Mills theory is studied on the lattice
using a new lattice fermion regulator, domain wall fermions. This formulation
even at non-zero lattice spacing does not require fine-tuning, has improved
chiral properties and can produce topological zero-mode phenomena. Numerical
simulations of the full theory on lattices with the topology of a torus
indicate the formation of a gluino condensate which is sustained at the chiral
limit. The condensate is non-zero even for small volume and small supersymmetry
breaking mass where zero mode effects due to gauge fields with fractional
topological charge appear to play a role.Comment: LaTeX, 35 pages, 11 eps figures. A few changes in sec. 5.3, figure 11
added. To appear in Phys. Rev.
Health problems and health care seeking behavior among adult backpackers while traveling in Thailand
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