The Chiral Extension of Lattice QCD

The chiral extension of Quantum Chromodynamics (XQCD) adds to the standard lattice action explicit pseudoscalar meson fields for the chiral condensates. With this action, it is feasible to do simulations at the chiral limit with zero mass Goldstone modes. We review the arguments for why this is expected to be in the same universality class as the traditional action. We present preliminary results on convergence of XQCD for naive fermions and on the methodology for introducing counter terms to restore chiral symmetry for Wilson fermions.Comment: 7 pages, LATTICE 94 talk by R. Brower: Latex file with 2 postscript figures for encapsulatio

Tracing the cosmic growth of supermassive black holes to z ∼ 3 with Herschel

We study a sample of Herschel selected galaxies within the Great Observatories Origins Deep Survey-South and the Cosmic Evolution Survey fields in the framework of the Photodetector Array Camera and Spectrometer (PACS) Evolutionary Probe project. Starting from the rich multiwavelength photometric data sets available in both fields, we perform a broad-band spectral energy distribution decomposition to disentangle the possible active galactic nucleus (AGN) contribution from that related to the host galaxy. We find that 37 per cent of the Herschel-selected sample shows signatures of nuclear activity at the 99 per cent confidence level. The probability of revealing AGN activity increases for bright (L_(1−1000) > 10^(11) L_⊙) star-forming galaxies at z > 0.3, becoming about 80 per cent for the brightest (L_(1−1000) > 10^(12) L_⊙) infrared (IR) galaxies at z ≥ 1. Finally, we reconstruct the AGN bolometric luminosity function and the supermassive black hole growth rate across cosmic time up to z ∼ 3 from a far-IR perspective. This work shows general agreement with most of the panchromatic estimates from the literature, with the global black hole growth peaking at z ∼ 2 and reproducing the observed local black hole mass density with consistent values of the radiative efficiency ϵ_(rad) (∼0.07)

Ion beam sputtering of silicon: Energy distributions of sputtered and scattered ions

The properties of sputtered and scattered ions are studied for ion beam sputtering of Si by bombardment with noble gas ions. The energy distributions in dependence on ion beam parameters (ion energy: 0.5-1 keV; ion species: Ne, Ar, Xe) and geometrical parameters (ion incidence angle, polar emission angle, and scattering angle) are measured by means of energy-selective mass spectrometry. The presence of anisotropic effects due to direct sputtering and scattering is discussed and correlated with process parameters. The experimental results are compared to calculations based on a simple elastic binary collision model and to simulations using the Monte-Carlo code sdtrimsp. The influence of the contribution of implanted primary ions on energy distributions of sputtered and scattered particles is studied in simulations. It is found that a 10% variation of the target composition leads to detectable but small differences in the energy distributions of scattered ions. Comparison with previously reported data for other ion/target configurations confirms the presence of similar trends and anisotropic effects: The number of high-energy sputtered ions increases with increasing energy of incident ions and decreasing scattering angle. The effect of the ion/target mass ratio is additionally investigated. Small differences are observed with the change of the primary ion species: The closer the mass ratio to unity, the higher the average energy of sputtered ions. The presence of peaks, assigned to different mechanisms of direct scattering, strongly depends on the ion/target mass ratio

Interplay between field-induced and frustration-induced quantum criticalities in the frustrated two-leg Heisenberg ladder

The antiferromagnetic Heisenberg two-leg ladder in the presence of frustration and an external magnetic field is a system that is characterized by two sorts of quantum criticalities, not only one. One criticality is the consequence of intrinsic frustration, and the other one is a result of the external magnetic field. So the behaviour of each of them in the presence of the other deserves to be studied. Using the Jordan-Wigner transformation in dimensions higher than one and bond-mean-field theory we examine the interplay between the field-induced and frustration-induced quantum criticalities in this system. The present work could constitute a prototype for those systems showing multiple, perhaps sometimes competing, quantum criticalities. We calculate several physical quantities like the magnetization and spin susceptibility as functions of field and temperature.Comment: 9 pages, 8 figures, submitted to the Canadian Journal of Physic

Numerical experiments with Bergman kernel functions in 2 and 3 dimensional cases

Pub. Int. CMAT, 1 (2003)In this paper we revisit the so-called Bergman kernel method - BKM- for solving conformal mapping problems and propose a generalized BKM-approach to extend the theory to 3-dimensional mapping problems. A special software package for quaternions was developed for the numerical experiments

Strongly coupled U(1) lattice gauge theory as a microscopic model of Yukawa theory

Dynamical chiral symmetry breaking in a strongly coupled U(1) lattice gauge model with charged fermions and scalar is investigated by numerical simulation. Several composite neutral states are observed, in particular a massive fermion. In the vicinity of the tricritical point of this model we study the effective Yukawa coupling between this fermion and the Goldstone boson. The perturbative triviality bound of Yukawa models is nearly saturated. The theory is quite similar to strongly coupled Yukawa models for sufficiently large coupling except the occurrence of an additional state -- a gauge ball of mass about half the mass of the fermion.Comment: 4 page

Applications of Bergman kernel functions

In this paper we revisit the so-called Bergman kernel method (BKM) for solving conformal mapping problems. This method is based on the reproducing property of the Bergman kernel function. The construction of reproducing kernel functions is not restricted to real dimension 2. Results concerning the construction of Bergman kernel functions in closed form for special domains in the framework of hypercomplex function theory suggest that BKM can also be extended to mapping problems in higher dimensions. We describe a 3-dimensional BKM-approach and present two numerical examples.Fundação para a Ciência e a Tecnologia (FCT) - Programa Operacional "Ciência, Tecnologia, Inovação" (POCTI)

The distinction between gastric ulceration and carcinoma of the stomach : value of the erythrocyte sedimentation rate and the maximal acid output

CITATION: Bock, O. A. A. & Boyd, I. H. 1973. The distinction between gastric ulceration and carcinoma of the stomach : value of the erythrocyte sedimentation rate and the maximal acid output. South African Medical Journal, 47(29):1259-1260.The original publication is available at http://www.samj.org.zaThe erythrocyte sedimentation rate (ESR) is not a reliable criterion for distinguishing between gastric ulceration and carcinoma of the stomach. If the maximal acid output (MAO) = 0 mEq/h, the lesion is, with few exceptions, a carcinoma. Combining the ESR and MAO did not provide a more reliable criterion for distinguishing between gastric ulcer and carcinoma of the stomach, than when MAO alone is taken into consideration.Publisher’s versio

Phase structure of the Higgs-Yukawa systems with chirally invariant lattice fermion actions

We develop analytical technique for examining phase structure of $Z_2$, $U(1)$, and $SU(2)$ lattice Higgs-Yukawa systems with radially frozen Higgs fields and chirally invariant lattice fermion actions. The method is based on variational mean field approximation. We analyse phase diagrams of such systems with different forms of lattice fermion actions and demonstrate that it crucially depends both on the symmetry group and on the form of the action. We discuss location in the diagrams of possible non-trivial fixed points relevant to continuum physics, and argue that the candidates can exist only in $Z_2$ system with SLAC action and $U(1)$ systems with naive and SLAC actions. [Note: By a product, missing term in Eq. (3.5) of hep-lat/9309010 is reconstructed, that, however, affects only the result of Sect. 4.3 (Fig. 3) of that reference (cf. Fig. 2(c) of this paper).]Comment: KEK-TH-390, KYUSHU-HET-17, 34 pages (harvmac) including 17 figures (appended in postscript format with uuencoded tar file).(PostScript Files are fixed.