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 $8^3 \times 32$ lattices at $\beta = 5.7$ 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

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

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

Structure and distribution of the slope fish community in the vicinity of the sub-Antarctic Prince Edward Archipelago

Demersal fish community structure, distribution and trophic relationships on the slope (depth range 200–1500 m) of the sub-Antarctic Prince Edward Islands and surrounding sea rises were investigated during a pilot survey conducted in April 2001 onboard fishing vessel MV Iris. A total of 56 fish taxa were collected during the survey, of which 44 were identified to the species level, seven to the genus level and five to the family level. Among the identified taxa, 36 constituted new records for the area investigated. Total catch per unit effort (cpue) during the survey ranged from 1•1 to 241•2 individuals h 1. Both average fish diversity and total cpue positively correlated with trawling depth. Overall, mean sampling depth and near-bottom temperature explained 56% of total fish cpue. Hierarchal cluster analysis identified three distinct fish assemblages with pronounced dominant species. Major shifts in fish community composition occurred at 500–600 m and 800–900 m depth strata and could probably be a result of physical and biological vertical zonation. Analysis of the diet of selected fish species showed that they were generalist feeders, consuming predominantly pelagic, including epipelagic, meso- and benthopelagic, prey. Diets of six species and nitrogen stable isotope signatures of 22 species revealed that with a few exceptions most fishes occupied the fourth trophic level and were tertiary consumers. Wide variability in carbon isotopic signatures is discussed with respect to alternative, e.g. possible importance of high Antarctic and chemoautotrophic v. photoautotrophic sub-Antarctic primary production, organic matter sources at the base of deep-sea food webs

Exploitation status of infralittoral abalone (Haliotis midae) and alikreukel (Turbo sarmaticus) in the southern section of the Eastern Cape coast, South Africa

Intertidal size-frequency distributions and densities for Haliotis midae and Turbo sarmaticus were examined at 10 sites experiencing varying pressure of human exploitation along the southern section of the Eastern Cape coast, South Africa. Target species' densities and maximum sizes were related both to the numbers of collectors on the shore and to indirect indicators of exploitation such as number of households in the vicinity and distance to the nearest beach access point. For both species, there was variation in density (P < 0.05) and size (P < 0.05) among sites, with densities ranging between 0.03-2.23 m^(-2) and 0.07-4.93 m^(-2) for H. midae and T. sarmaticus, respectively. Maximum sizes ranged between 49.4-153.5 mm (H. midae) and 28.3-104.4 mm (T. sarmaticus) shell length. Population parameters such as mean maximum size and total density were significantly negatively related to exploitation indicators for both species. In addition, densities of sexually mature and legal-size individuals of T. sarmaticus were significantly negatively related to the number of households. However, only for H. midae were densities of subadults significantly negatively related to the number of collectors, suggesting that reproduction of abalone may be suppressed at the most exploited sites. Exploitation of T. sarmaticus tends to be localized near population centres, whereas H. midae is collected over a larger range of sites. Overall, T. sarmaticus is less affected by exploitation than H. midae

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

Interleukin-9 (IL-9) and NPM-ALK each generate mast cell hyperplasia as single ‘hit’ and cooperate in producing a mastocytosis-like disease in mice

Mast cell neoplasms are characterized by abnormal growth and focal accumulation of mast cells (MC) in one or more organs. Although several cytokines, including stem cell factor (SCF) and interleukin-9 (IL-9) have been implicated in growth of normal MC, little is known about pro-oncogenic molecules and conditions triggering differentiation and growth of MC far enough to lead to the histopathological picture of overt mastocytosis. The anaplastic lymphoma kinase (ALK) has recently been implicated in growth of neoplastic cells in malignant lymphomas. Here, we describe that transplantation of NPM-ALK-transplanted mouse bone marrow progenitors into lethally irradiated IL-9 transgenic mice not only results in lymphoma-formation, but also in the development of a neoplastic disease exhibiting histopathological features of systemic mastocytosis, including multifocal dense MC-infiltrates, occasionally with devastating growth in visceral organs. Transplantation of NPM-ALK-transduced progenitors into normal mice or maintaintence of IL-9-transgenic mice without NPM-ALK each resulted in MC hyperplasia, but not in mastocytosis. Neoplastic MC in mice not only displayed IL-9, but also the IL-9 receptor, and the same was found to hold true for human neoplastic MC. Together, our data show that neoplastic MC express IL-9 rececptors, that IL-9 and NPM-ALK upregulate MC-production in vivo, and that both ‘hits’ act in concert to induce a mastocytosis-like disease in mice. These data may have pathogenetic and clinical implications and fit well with the observation that neoplastic MC in advanced SM strongly express NPM and multiple “lymphoid” antigens including CD25 and CD30

Domain Wall Fermions in Quenched Lattice QCD

We study the chiral properties and the validity of perturbation theory for domain wall fermions in quenched lattice QCD at beta=6.0. The explicit chiral symmetry breaking term in the axial Ward-Takahashi identity is found to be very small already at Ns=10, where Ns is the size of the fifth dimension, and its behavior seems consistent with an exponential decay in Ns within the limited range of Ns we explore. From the fact that the critical quark mass, at which the pion mass vanishes as in the case of the ordinary Wilson-type fermion, exists at finite Ns, we point out that this may be a signal of the parity broken phase and investigate the possible existence of such a phase in this model at finite Ns. The rho and pi meson decay constants obtained from the four-dimensional local currents with the one-loop renormalization factor show a good agreement with those obtained from the conserved currents

Quenched Lattice QCD with Domain Wall Fermions and the Chiral Limit

Quenched QCD simulations on three volumes, $8^3 \times$, $12^3 \times$ and $16^3 \times 32$ and three couplings, $\beta=5.7$, 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 ($L_s$) is increased. However, at stronger couplings much larger values of $L_s$ are required to achieve a given physical value of \mres. For $\beta=6.0$ and $L_s=16$, we find \mres/m_s=0.033(3), while for $\beta=5.7$, and $L_s=48$, \mres/m_s=0.074(5), where $m_s$ 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 $m_\pi^2$ 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 $f_\pi$ 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