On QCD and Effective Locality

In a recent paper it was shown how quark scattering in a quenched, eikonal model led to a momentum-transfer dependent amplitude expressed in terms of Halpern's functional integral; and how the requirement of manifest gauge invariance converted that functional integral into a local integral, capable of being evaluated with precision by a finite set of numerical integrations. We here prove that this property of "effective locality" holds true for all quark processes, without approximation and without exception.Comment: Expanded and Revised in REVTeX 4.1, 14 pages, follow-on work of Eur. Phys. J. C65, pp.395-411 (2010) or arXiv:0903.2644v2 [hep-th

Sodium vacancy ordering and the co-existence of localized spins and itinerant charges in NaxCoO2

The sodium cobaltate family (NaxCoO2) is unique among transition metal oxides because the Co sits on a triangular lattice and its valence can be tuned over a wide range by varying the Na concentration x. Up to now detailed modeling of the rich phenomenology (which ranges from unconventional superconductivity to enhanced thermopower) has been hampered by the difficulty of controlling pure phases. We discovered that certain Na concentrations are specially stable and are associated with superlattice ordering of the Na clusters. This leads naturally to a picture of co-existence of localized spins and itinerant charge carriers. For x = 0.84 we found a remarkably small Fermi energy of 87 K. Our picture brings coherence to a variety of measurements ranging from NMR to optical to thermal transport. Our results also allow us to take the first step towards modeling the mysterious ``Curie-Weiss'' metal state at x = 0.71. We suggest the local moments may form a quantum spin liquid state and we propose experimental test of our hypothesis.Comment: 16 pages, 5 figure

The PARSE Programming Paradigm. Part I: Software Development Methodology. Part II: Software Development Support Tools

The programming methodology of PARSE (parallel software environment), a software environment being developed for reconfigurable non-shared memory parallel computers, is described. This environment will consist of an integrated collection of language interfaces, automatic and semi-automatic debugging and analysis tools, and operating system —all of which are made more flexible by the use of a knowledge-based implementation for the tools that make up PARSE. The programming paradigm supports the user freely choosing among three basic approaches /abstractions for programming a parallel machine: logic-based descriptive, sequential-control procedural, and parallel-control procedural programming. All of these result in efficient parallel execution. The current work discusses the methodology underlying PARSE, whereas the companion paper, “The PARSE Programming Paradigm — II: Software Development Support Tools,” details each of the component tools

Flux through a hole from a shaken granular medium

We have measured the flux of grains from a hole in the bottom of a shaken container of grains. We find that the peak velocity of the vibration, vmax, controls the flux, i.e., the flux is nearly independent of the frequency and acceleration amplitude for a given value of vmax. The flux decreases with increasing peak velocity and then becomes almost constant for the largest values of vmax. The data at low peak velocity can be quantitatively described by a simple model, but the crossover to nearly constant flux at larger peak velocity suggests a regime in which the granular density near the container bottom is independent of the energy input to the system.Comment: 14 pages, 4 figures. to appear in Physical Review