82 research outputs found

    Gravitons in One-Loop Quantum Cosmology: Correspondence Between Covariant and Non-Covariant Formalisms

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    The discrepancy between the results of covariant and non-covariant one-loop calculations for higher-spin fields in quantum cosmology is analyzed. A detailed mode-by-mode study of perturbative quantum gravity about a flat Euclidean background bounded by two concentric 3-spheres, including non-physical degrees of freedom and ghost modes, leads to one-loop amplitudes in agreement with the covariant Schwinger-DeWitt method. This calculation provides the generalization of a previous analysis of fermionic fields and electromagnetic fields at one-loop about flat Euclidean backgrounds admitting a well-defined 3+1 decomposition.Comment: 29 pages, latex, recently appearing in Physical Review D, volume 50, pages 6329-6337, November 1994. The authors apologize for the delay in circulating the paper, due to technical problems now fixe

    Stabilization and pumping of giant vortices in dilute Bose-Einstein condensates

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    Recently, it was shown that giant vortices with arbitrarily large quantum numbers can possibly be created in dilute Bose-Einstein condensates by cyclically pumping vorticity into the condensate. However, multiply quantized vortices are typically dynamically unstable in harmonically trapped nonrotated condensates, which poses a serious challenge to the vortex pump procedure. In this theoretical study, we investigate how the giant vortices can be stabilized by the application of a Gaussian potential peak along the vortex core. We find that achieving dynamical stability is feasible up to high quantum numbers. To demonstrate the efficiency of the stabilization method, we simulate the adiabatic creation of an unsplit 20-quantum vortex with the vortex pump.Comment: 8 pages, 6 figures; to be published in J. Low Temp. Phys., online publication available at http://dx.doi.org/10.1007/s10909-010-0216-

    Relativistic Gauge Conditions in Quantum Cosmology

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    This paper studies the quantization of the electromagnetic field on a flat Euclidean background with boundaries. One-loop scaling factors are evaluated for the one-boundary and two-boundary backgrounds. The mode-by-mode analysis of Faddeev-Popov quantum amplitudes is performed by using zeta-function regularization, and is compared with the space-time covariant evaluation of the same amplitudes. It is shown that a particular gauge condition exists for which the corresponding operator matrix acting on gauge modes is in diagonal form from the beginning. Moreover, various relativistic gauge conditions are studied in detail, to investigate the gauge invariance of the perturbative quantum theory.Comment: 26 pages, plain TeX, no figure

    Observation of a decoupled band in 123 Cs

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    The methods of in-beam Îł -ray spectroscopy have been used to study 123 Cs produced by the 115 In( 12 C, 4 n ) reaction. Five coincident stretched E 2 transitions, previously assigned in the literature to 123 Ba, have been identified as members of a decoupled band in 123 Cs.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45822/1/10050_2005_Article_BF01422105.pd

    Evaluation of whole-body vibration exposures in British industry

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    This report describes measurements of whole-body vibration on eight excavators and two compact skid-steer loaders. Of the excavators, four were fitted with impact hammers, two with hydraulic crushers, one with a backhoe shovel and one with steel shears.Accelerations were measured on the seat surface and on the floor within the operators’ cabs of the machines in accordance with ISO 2631 (1997). The data have been evaluated in the context of the levels set out in the European Union Physical Agents (Vibration) Directive (2002/44/EC). The report provides predicted daily vibration exposure for each machine. The effects of machine operation and other parameters on the vibration exposures are also considered.This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.<br/
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