3,191 research outputs found

    Mean link versus average plaquette tadpoles in lattice NRQCD

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    We compare mean-link and average plaquette tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. Simulations are done for the three quarkonium systems ccˉc\bar c, bcˉb\bar c, and bbˉb\bar b. The hyperfine splittings are computed both at leading and at next-to-leading order in the relativistic expansion. Results are obtained at a large number of lattice spacings. A number of features emerge, all of which favor tadpole renormalization using mean links. This includes much better scaling of the hyperfine splittings in the three quarkonium systems. We also find that relativistic corrections to the spin splittings are smaller with mean-link tadpoles, particularly for the ccˉc\bar c and bcˉb\bar c systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about one in lattice units (with the bare quark masses turning out to be much larger with mean-link tadpoles).Comment: LATTICE(heavyqk) 3 pages, 2 figure

    Seismological Investigations Of Plate Tectonics In South-Central Alaska

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    Thesis (Ph.D.) University of Alaska Fairbanks, 197

    Identifying ILI Cases from Chief Complaints: Comparing the Accuracy of Keyword and Support Vector Machine Methods

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    We compared the accuracy of two methods of identifying ILI cases from chief complaints. We found that a support vector machine method was more accurate than a keyword method

    The Multicultural Classroom: Plan, Build, Renew - Librarian as Constructivist Architect

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    Of New York State’s largest urban school districts, Rochester ranks lowest with an appalling graduation rate of 39%.1 With goals of keeping our poorest children in school and focusing their futures on college, SUNY Geneseo hosted 50 young “CSI candidates” who worked tirelessly to solve fictitious art thefts. Library research, blogging, public speaking, interviewing, forensic science, and digital photography were among the skills incorporated, forming a solid base of critical literacy for these young scholars. Milne Library helped create an educational yet recreational learning environment by offering instructors, classroom space, technology, potential suspects, and ultimately, one of the indicted “criminals.” Susan Norman will offer the overarching goals of the RYSAG (Rochester Young Scholars Academy at Geneseo) program, the results of our efforts, and plans for the future. Kim Davies Hoffman will bring focus to the importance of libraries and librarians in the struggle to keep children (specifically those from the inner city) in school and aiming high towards a successful future. 1. Who’ll lead city schools, Rochester Democrat & Chronicle, 10/27/0

    Tadpole renormalization and relativistic corrections in lattice NRQCD

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    We make a comparison of two tadpole renormalization schemes in the context of the quarkonium hyperfine splittings in lattice NRQCD. Improved gauge-field and NRQCD actions are analyzed using the mean-link u0,Lu_{0,L} in Landau gauge, and using the fourth root of the average plaquette u0,Pu_{0,P}. Simulations are done for ccˉc\bar c, bcˉb\bar c, and bbˉb\bar b systems. The hyperfine splittings are computed both at leading and at next-to-leading order in the relativistic expansion. Results are obtained at lattice spacings in the range of about 0.14~fm to 0.38~fm. A number of features emerge, all of which favor tadpole renormalization using u0,Lu_{0,L}. This includes much better scaling behavior of the hyperfine splittings in the three quarkonium systems when u0,Lu_{0,L} is used. We also find that relativistic corrections to the spin splittings are smaller when u0,Lu_{0,L} is used, particularly for the ccˉc\bar c and bcˉb\bar c systems. We also see signs of a breakdown in the NRQCD expansion when the bare quark mass falls below about one in lattice units. Simulations with u0,Lu_{0,L} also appear to be better behaved in this context: the bare quark masses turn out to be larger when u0,Lu_{0,L} is used, compared to when u0,Pu_{0,P} is used on lattices with comparable spacings. These results also demonstrate the need to go beyond tree-level tadpole improvement for precision simulations.Comment: 14 pages, 7 figures (minor changes to some phraseology and references

    A review of Turboelectric Distributed Propulsion technologies for N+3 aircraft electrical systems

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    In order to minimise the environmental impact of increased air traffic substantial developments in civil aircraft electrical power systems must occur. NASA have set a target to reduce noise by 71dB, NOx emissions by 80% and fuel consumption by 60% for the N+3 generation of aircraft entering into service sometime between 2030 and 2035. Turboelectric Distributed Propulsion (TeDP) is expected to enable these goals to be met. NASA's N3-X concept aircraft comprises gas turbine engines which drive electrical generators and a DC network distributes power to an array of fans, which provide thrust. Interconnection and protection technologies will also be included to achieve desired levels of reliability of supply to the propulsion motors. This paper outlines the architecture of a generic TeDP system, explores its benefits, describes technical challenges that will need to be overcome and discusses the technical implications of implementing TeDP with regards to electrical system power density and safety

    The Biermann Battery in Cosmological MHD Simulations of Population III Star Formation

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    We report the results of the first self-consistent three-dimensional adaptive mesh refinement magnetohydrodynamical simulations of Population III star formation including the Biermann Battery effect. We find that the Population III stars formed including this effect are both qualitatively and quantitatively similar to those from hydrodynamics-only (non-MHD) cosmological simulations. We observe peak magnetic fields of ~10^-9 G in the center of our star-forming halo at z ~ 17.55. The magnetic fields created by the Biermann Battery effect are predominantly formed early in the evolution of the primordial halo at low density and large spatial scales, and then grow through compression and by shear flows. The fields seen in this calculation are never large enough to be dynamically important (with beta >= 10^{15} at all times), and should be considered the minimum possible fields in existence during Population III star formation, and may be seed fields for the stellar dynamo or the magnetorotational instability at higher densities and smaller spatial scales.Comment: 4 pages, 3 figures; Submitted to the Astrophysical Journal Letters. Comments welcome. Typo found (and fixed) in equation
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