Calculation of electronic properties of amorphous alloys

We describe the application of the locally-self-consistent-multiple-scattering (LSMS)[1] method to amorphous alloys. The LSMS algorithm is optimized for the Intel XP/S-150, a multiple-instruction-multiple-data parallel computer with 1024 nodes and 2 compute processors per node. The electron density at each site is determined by solving the multiple scattering equation for atoms within a specified distance of the atom under consideration. Because this method is carried out in real space it is ideal for treating amorphous alloys. We have adapted the code to the calculation of the electronic properties of amorphous alloys. In these calculations we determine the potentials in the atomic sphere approximation self consistently at each site, unlike previous calculations[2] where we determined the potentials self consistently at an average site. With these self-consistent potentials, we then calculate electronic properties of various amorphous alloy systems. We present calculated total electronic densities of states for amorphous Ni$_{80}$P$_{20}$ and Ni$_{40}$Pd$_{40}$P$_{20}$ with 300 atoms in a supercell.Comment: 10 pages, plain tex, 2 figures. Paper accepted for publication in Proceedings of LAM-9 and Journal of non-Crystalline Solids. Please request preprints from J.C. Swihart ([email protected]

Evolution of Parton Fragmentation Functions at Finite Temperature

The first order correction to the parton fragmentation functions in a thermal medium is derived in the leading logarithmic approximation in the framework of thermal field theory. The medium-modified evolution equations of the parton fragmentation functions are also derived. It is shown that all infrared divergences, both linear and logarithmic, in the real processes are canceled among themselves and by corresponding virtual corrections. The evolution of the quark number and the energy loss (or gain) induced by the thermal medium are investigated.Comment: 21 pages in RevTex, 10 figure

Spin transport of electrons through quantum wires with spatially-modulated strength of the Rashba spin-orbit interaction

We study ballistic transport of spin-polarized electrons through quantum wires in which the strength of the Rashba spin-orbit interaction (SOI) is spatially modulated. Subband mixing, due to SOI, between the two lowest subbands is taken into account. Simplified approximate expressions for the transmission are obtained for electron energies close to the bottom of the first subband and near the value for which anticrossing of the two lowest subbands occurs. In structures with periodically varied SOI strength, {\it square-wave} modulation on the spin transmission is found when only one subband is occupied and its possible application to the spin transistor is discussed. When two subbands are occupied the transmission is strongly affected by the existence of SOI interfaces as well as by the subband mixing

Transverse instability and its long-term development for solitary waves of the (2+1)-Boussinesq equation

The stability properties of line solitary wave solutions of the (2+1)-dimensional Boussinesq equation with respect to transverse perturbations and their consequences are considered. A geometric condition arising from a multi-symplectic formulation of this equation gives an explicit relation between the parameters for transverse instability when the transverse wavenumber is small. The Evans function is then computed explicitly, giving the eigenvalues for transverse instability for all transverse wavenumbers. To determine the nonlinear and long time implications of transverse instability, numerical simulations are performed using pseudospectral discretization. The numerics confirm the analytic results, and in all cases studied, transverse instability leads to collapse.Comment: 16 pages, 8 figures; submitted to Phys. Rev.

High performance Beowulf computer for lattice QCD

We describe the construction of a high performance parallel computer composed of PC components, as well as the performance test in lattice QCD.Comment: Lattice 2001 (Algorithms and Machines) 3 page

Tendencias políticas en disputa para la gobernanza global del acaparamiento de tierras

La expansión de los ‘cultivos y materias primas flexibles’ en el marco de una transición paulatina en el régimen alimentario global, junto a la emergencia de los países BRICS y MICS (de Renta Media) y el revalorizado papel de los estados nación, conforman un contexto crítico para el acaparamiento de tierras. Estas transformaciones globales que determinan, y son a su vez determinadas por, el actual acaparamiento global de tierras, han resultado en varias interpretaciones en disputa alrededor de su significado, complejizando aún más el ya de por si complejo terreno de la gobernanza. Estamos siendo testigos de una disputa política tripartita sobre el control del carácter, ritmo, parámetros y trayectoria discursiva, así como de los instrumentos sobre, y la práctica de, la gobernanza global del acaparamiento de tierras, como en el caso de las Directrices Voluntarias del Comité de Seguridad Alimentaria Mundial de la ONU. Esta contienda gira alrededor de las siguientes tres tendencias: ‘regular para facilitar’, ‘regular para mitigar impactos negativos y maximizar oportunidades’, y ‘regular para detener y revertir’ el acaparamiento de tierras. Las trayectorias futuras del acaparamiento de tierras serán determinadas en buena medida por el balance entre fuerzas sociales y estatales en cada una y entre las tres tendencias políticas. Este artículo plantea un análisis preliminar a partir del mapeo de áreas de indagación sub-exploradas y ofrece más una serie de modos de cuestionamiento inicial, que argumentos firmes basados en material empírico sólido y completo