Jon Flower

The field distribution in SU(3) lattice gauge theory

Abstract We have measured the distribution of energy density in the chromo-electric and chromo-magnetic fields produced by a static quark-anti-quark pair. We find that the dominant contribution is in the form of a thin tube of chromo-electric flux between the sources while there are both electric and magnetic contributions in transverse directions which are interpreted as being consistent with an oscillating, thin string.

Moose: a multi-tasking operating system of hypercubes

The MOOSE project was begun at Caltech in Summer 1986. Its goal is to produce a powerful, flexible multi-tasking operating system suitable for research into load-balancing and decomposition of irregular and dynamic problems. Sec. 2 of this report describes the features of the MOOSE system in some detail. In Sec. 3 we discuss where we expect developments in MOOSE to take place, and in Sec. 4 we review some of the lessons learned from the MOOSE project.

Parallel programming in comfort

We describe a set of software utilities designed to facilitate the writing of parallel codes and porting sequential ones. Emphasis is placed on portability so that code can be developed simultaneously on a sequential and a parallel machine, and so that the completed code can be run and maintained on a wide variety of machine architectures. We describe the CrOS communication package for parallel machines, the CUBIX system to allow a code to run in parallel or sequentially, the PLOTIX parallel graphics foundation, and the parallel debugger NDB. While the system described has been implemented on qualitatively different machines the particular version described here is most efficient for the hypercube architecture, and was developed on NCUBE hypercubes under both the AXIS or XENIX operating systems.

Finite-element analysis on a PC

The authors describe how they achieved mainframe performance by coding the Cosmos/M finite-element analysis system, a commercial product, for a PC enhanced with a parallel-processing board. The discussion covers design goals, algorithm design, implementation and debugging, performance optimization, and scalability. They focus on financial, algorithmic, and numerical issues, with almost no reference to the numerical principles involved in solving stress-analysis equations.<<ETX>>

Systematic errors in Monte Carlo methods for fermions

Abstract The systematic errors introduced by various simulation methods for including dynamical fermions into lattice gauge Monte Carlo are analyzed. In particular, we find that a discretization of the Langevin equation leads to relative errors of order δτξ2, where ξ is the lattice correlation length.

Baryons on the lattice

Abstract A detailed study of heavy baryons is performed via Monte Carlo lattice gauge theory. Studying the off-axis qq potential we assess the effect of discrete rotational symmetry on physical parameters such as the string tension. At β = 6.1 these are of order 15% but seem insignificant at β = 6.3. The baryonic potential is calculated and yields a string tension comparable to that observed in mesonic Monte Carlo calculations as well as that derived from Regge slopes and relativised hadronic models. It is suggested that the effects of string vibrations are small in the range x ⪅ 0.5 fm. The baryonic energy density is also studied and strongly supports the dual superconductor model of confinement as well as suggesting that the baryonic strings meet at a single central point rather than joining the quarks pairwise.