Hadron Mass Extraction from Lattice QCD

The extraction of quantities from lattice QCD calculations at realistic quark masses is of considerable importance. Whilst physical quark masses are some way off, the recent advances in the calculation of hadron masses within full QCD now invite improved extrapolation methods. We show that, provided the correct chiral behaviour of QCD is respected in the extrapolation to realistic quark masses, one can indeed obtain a fairly reliable determination of masses, the sigma commutator and the J parameter. We summarise these findings by presenting the nonanalytic behaviour of nucleon and rho masses in the standard Edinburgh plot.Comment: Talk presented by S. V. Wright at the Workshop on Lattice Hadron Physics (LHP2001), Cairns, Australia, 9-18 July 2001, 8 pages, requires espcrc2.sty (included

A 15-Kiloparsec X-Ray Disk in the Elliptical Galaxy NGC 1700

We present Chandra observations of the young elliptical galaxy NGC 1700. The X-ray isophotes are highly flattened between semimajor axes of 30 and 80 arcseconds, reaching a maximum ellipticity of approximately 0.65 at 60 arcsec (15 kpc). The surface brightness profile in the spectrally soft, flattened region is shallower than that of the starlight, indicating that the emission comes from hot gas rather than stellar sources. The flattening is so extreme that the gas cannot be in hydrostatic equilibrium in any plausible potential. A likely alternative is that the gas has significant rotational support. A simple model, representing isothermal gas distributed about a particular angular momentum, can reproduce the X-ray morphology while staying consistent with stellar kinematics. The specific angular momentum of the gas matches that of the stars in the most isophotally distorted outer part of the galaxy, and its cooling time matches the time since the last major merger. We infer that the gas was acquired in that merger, which involved a pre-existing elliptical galaxy with a hot ISM. The hot gas carried the angular momentum of the encounter, and has since gradually settled into a rotationally flattened, cooling disk.Comment: 11 pages, 2 figures, AASTeX 5.0. Accepted for publication in The Astrophysical Journa

Spin Hall Conductance of the Two Dimensional Hole Gas in a Perpendicular Magnetic Field

The charge and spin Hall conductance of the two-dimensional hole gas within the Luttinger model with and without inversion symmetry breaking terms in a perpendicular magnetic field are studied, and two key phenomena are predicted. The sign of the spin Hall conductance is modulated periodically by the external magnetic field, which means a possible application in the future. Furthermore, a resonant spin Hall conductance in the two-dimensional hole gas with a certain hole density at a typical magnetic field is indicated, which implies a likely way to firmly establish the intrinsic spin Hall effect. The charge Hall conductance is unaffected by the spin-orbit coupling.Comment: accepted for publication in Phys. Rev. B; 6 pages, 4 figure

Developing a partcipatory approach to seed production and varietal selection

The performance of UK winter wheat varieties was tested under organic conditions involving farmer participation. Three breadmaking varieties (Hereward, Solstice and Xi19) and their mixture (1:1:1) were grown at 19 UK farms in 2003/04 and 2004/05. The variability of productivity on organic farms was illustrated with more variation among farm sites than among varieties. Seed health was generally high over all sites. Although the trials were successful, more time was needed at project initiation to improve farmer involvement. Some farmers expected more researcher visits, and were reticent about assessing the trials themselves. In contrast, some participants valued the variety performance data on their farms particularly when related to that of other growers. The balance between the goals of the researchers relative to the farmers needs to be defined at project initiation

Charged-Particle Motion in Electromagnetic Fields Having at Least One Ignorable Spatial Coordinate

We give a rigorous derivation of a theorem showing that charged particles in an arbitrary electromagnetic field with at least one ignorable spatial coordinate remain forever tied to a given magnetic-field line. Such a situation contrasts the significant motions normal to the magnetic field that are expected in most real three-dimensional systems. It is pointed out that, while the significance of the theorem has not been widely appreciated, it has important consequences for a number of problems and is of particular relevance for the acceleration of cosmic rays by shocks.Comment: 7 pages, emulateapj format, including 1 eps figure, to appear in The Astrophysical Journal, Dec. 10 1998 issu