QCDF90: Lattice QCD with Fortran 90

We have used Fortran 90 to implement lattice QCD. We have designed a set of machine independent modules that define fields (gauge, fermions, scalars, etc...) and overloaded operators for all possible operations between fields, matrices and numbers. With these modules it is very simple to write high-level efficient programs for QCD simulations. To increase performances our modules also implements assignments that do not require temporaries, and a machine independent precision definition. We have also created a useful compression procedure for storing the lattice configurations, and a parallel implementation of the random generators. We have widely tested our program and modules on several parallel and single processor supercomputers obtaining excellent performances.Comment: LaTeX file, 8 pages, no figures. More information available at: http://hep.bu.edu/~leviar/qcdf90.htm

Phase Diagram of a Classical Fluid in a Quenched Random Potential

We consider the phase diagram of a classical fluid in the presence of a random pinning potential of arbitrary strength. Introducing replicas for averaging over the quenched disorder, we use the hypernetted chain approximation to calculate the correlations in the replicated liquid. The freezing transition of the liquid into a nearly crystalline state is studied using a density functional approach, and the liquid-to-glass transition is studied using a phenomenological replica symmetry breaking approach introduced by Mezard and Parisi. The first-order liquid-to-crystal transition is found to change to a continuous liquid-to-glass transition as the strength of the disorder is increased above a threshold value.Comment: 7 pages, 4 figures, to appear in EuroPhysics Letter

Spatial persistence and survival probabilities for fluctuating interfaces

We report the results of numerical investigations of the steady-state (SS) and finite-initial-conditions (FIC) spatial persistence and survival probabilities for (1+1)--dimensional interfaces with dynamics governed by the nonlinear Kardar--Parisi--Zhang (KPZ) equation and the linear Edwards--Wilkinson (EW) equation with both white (uncorrelated) and colored (spatially correlated) noise. We study the effects of a finite sampling distance on the measured spatial persistence probability and show that both SS and FIC persistence probabilities exhibit simple scaling behavior as a function of the system size and the sampling distance. Analytical expressions for the exponents associated with the power-law decay of SS and FIC spatial persistence probabilities of the EW equation with power-law correlated noise are established and numerically verified.Comment: 11 pages, 5 figure

Third-Generation TB-LMTO

We describe the screened Korringa-Kohn-Rostoker (KKR) method and the third-generation linear muffin-tin orbital (LMTO) method for solving the single-particle Schroedinger equation for a MT potential. The simple and popular formalism which previously resulted from the atomic-spheres approximation (ASA) now holds in general, that is, it includes downfolding and the combined correction. Downfolding to few-orbital, possibly short-ranged, low-energy, and possibly orthonormal Hamiltonians now works exceedingly well, as is demonstrated for a high-temperature superconductor. First-principles sp3 and sp3d5 TB Hamiltonians for the valence and lowest conduction bands of silicon are derived. Finally, we prove that the new method treats overlap of the potential wells correctly to leading order and we demonstrate how this can be exploited to get rid of the empty spheres in the diamond structure.Comment: latex2e, 32 printed pages, Postscript figs, to be published in: Tight-Binding Approach to Computational Materials Science, MRS Symposia Proceedings No. 491 (MRS, Pittsburgh, 1998

CONSUMER PERCEPTIONS OF TROUT AS A FOOD ITEM

The impacts of socioeconomic/demographic characteristics, experiences and preferences of consumers on trout purchasing decisions were estimated using Probit and Ordered Probit regression techniques. Data from a survey of consumer purchasing behavior and personal attributes were used to deduce factors that led to either a high or low likelihood of purchasing trout products. Analysis of data pertaining to whole trout and value-added products yielded consistently different characteristics of consumers who show a high affinity toward purchasing one or more of such products. Results from these analyses were used to suggest techniques for marketing whole trout and value-added trout products to specific segments of the consumer population.Food Consumption/Nutrition/Food Safety,

The Taming of QCD by Fortran 90

We implement lattice QCD using the Fortran 90 language. We have designed machine independent modules that define fields (gauge, fermions, scalars, etc...) and have defined overloaded operators for all possible operations between fields, matrices and numbers. With these modules it is very simple to write QCD programs. We have also created a useful compression standard for storing the lattice configurations, a parallel implementation of the random generators, an assignment that does not require temporaries, and a machine independent precision definition. We have tested our program on parallel and single processor supercomputers obtaining excellent performances.Comment: Talk presented at LATTICE96 (algorithms) 3 pages, no figures, LATEX file with ESPCRC2 style. More information available at: http://hep.bu.edu/~leviar/qcdf90.htm

TROUT STEAKS: CONSUMER PERCEPTIONS OF A NEW FOOD ITEM

Water quality standards and a limited water supply have dramatically restricted the expansion of the U.S. trout industry. Faced with production restrictions, producers have turned to value-added products to strengthen the economic growth of the industry. In the near future, trout steaks could surface in retail outlets as a new revenue source for the mature trout industry. A telephone survey of consumers in Chicago and Los Angeles was conducted by the University of Idaho in the spring of 1997 to determine consumer preferences for trout steaks and, ultimately, to determine the viability of this product form. Using a probit analysis, fresh trout steaks were found to be more popular than frozen trout steaks. Consumers that exhibited significantly higher preference for fresh trout steaks were Hispanic, had high school education (or less), and/or believed that trout was less expensive than other meats. Chicago respondents and individuals with an urban background tended to display a higher preference toward frozen trout steaks.Consumer/Household Economics,

Instability, Intermittency and Multiscaling in Discrete Growth Models of Kinetic Roughening

We show by numerical simulations that discretized versions of commonly studied continuum nonlinear growth equations (such as the Kardar-Parisi-Zhang equation and the Lai-Das Sarma equation) and related atomistic models of epitaxial growth have a generic instability in which isolated pillars (or grooves) on an otherwise flat interface grow in time when their height (or depth) exceeds a critical value. Depending on the details of the model, the instability found in the discretized version may or may not be present in the truly continuum growth equation, indicating that the behavior of discretized nonlinear growth equations may be very different from that of their continuum counterparts. This instability can be controlled either by the introduction of higher-order nonlinear terms with appropriate coefficients or by restricting the growth of pillars (or grooves) by other means. A number of such ``controlled instability'' models are studied by simulation. For appropriate choice of the parameters used for controlling the instability, these models exhibit intermittent behavior, characterized by multiexponent scaling of height fluctuations, over the time interval during which the instability is active. The behavior found in this regime is very similar to the ``turbulent'' behavior observed in recent simulations of several one- and two-dimensional atomistic models of epitaxial growth. [pacs{61.50.Cj, 68.55.Bd, 05.70.Ln, 64.60.Ht}]Comment: 47 pages + 26 postscript figures, submitted to Phys. Rev.

Microstructured cladding elements to enhance performance and flexibility of large mode area leakage channel fibers

Large mode area fibers are imperative for scaling up the average power of fiber lasers. Single-mode behavior and low FM loss are the crucial functionalities for these fibers. However, for key applications such as picosecond pulsed lasers, the device length needs to at least a few meters. This makes a certain degree of bend tolerance a prerequisite in the fiber design. While rod-type PCFs have been very successful in offering large mode areas, their rigid configuration limits their application domain. Alternatively, leakage channel fibers (LCFs) have shown a great potential for offering substantial bend tolerance along with large mode areas. However, the proposed use of Fluorine-doped rods in the all-solid version limits their practical design space. Here, we propose a novel design concept to attain single-material, large mode area fibers (mode area >~ 1000µm2) with effectively single mode operation coupled with bending characteristics comparable to all-solid LCFs and greater design flexibility and easier splicing that is comparable to rod-type PCFs

Structure and Magnetization of Two-Dimensional Vortex Arrays in the Presence of Periodic Pinning

Ground-state properties of a two-dimensional system of superconducting vortices in the presence of a periodic array of strong pinning centers are studied analytically and numerically. The ground states of the vortex system at different filling ratios are found using a simple geometric argument under the assumption that the penetration depth is much smaller than the spacing of the pin lattice. The results of this calculation are confirmed by numerical studies in which simulated annealing is used to locate the ground states of the vortex system. The zero-temperature equilibrium magnetization as a function of the applied field is obtained by numerically calculating the energy of the ground state for a large number of closely spaced filling ratios. The results show interesting commensurability effects such as plateaus in the B-H diagram at simple fractional filling ratios.Comment: 12 pages, 19 figures, submitted for publicatio