3,376 research outputs found

    Self-Similar Random Processes and Infinite-Dimensional Configuration Spaces

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    We discuss various infinite-dimensional configuration spaces that carry measures quasiinvariant under compactly-supported diffeomorphisms of a manifold M corresponding to a physical space. Such measures allow the construction of unitary representations of the diffeomorphism group, which are important to nonrelativistic quantum statistical physics and to the quantum theory of extended objects in d-dimensional Euclidean space. Special attention is given to measurable structure and topology underlying measures on generalized configuration spaces obtained from self-similar random processes (both for d = 1 and d > 1), which describe infinite point configurations having accumulation points

    Spirometry of healthy adult South African men

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    Aim. To detennine normative spirometric values for black and white South African men.Methods. A population of 796 bank personnel were subjected to spirometry and anthropometric measurements. An exhaustive questionnaire and radiographic screening process was used to identify a healthy population. Spirometry was performed using two calibrated instruments, a sleeve sealed piston spirometer (Autolink) and a bellows spirometer (Vitalograph). The methodological guidelines of the American Thoracic Society were observed. In the regression analysis Mallow's CP statistic was used to identify the best prediction models.Results. Compelling evidence was found in support of incorporating sitting height in prediction equations. For the Autolink studies the prediction equations (based on age, slanding height and weight) for forced vital capacity (FVC) (litres) were as follows: blacks: 0.053 height- 0.030 age 3.54; and whites: 0.056 height - 0.038 age - 3.07; for forced expiratory volume in the 1st second (FEV,) (litres) blacks: 0.038 height- 0.032 age - 1.18; and whites: 0.042 height- 0.038 age - 1.45. For the VitaJograph the equations were: FVC: blacks 0.048 height - 0.024 age 3.08 L; whites 0.056 height- 0.031 age - 3.42; FEV,: blacks 0.029 height - 0.027 age - 0.535; whites 0.042 height- 0.036 age - 1.84.Conclusion. The VitaJograph yielded significantly lower values than the Autolink for FVC measurements despite absolute consistency in methods. In view of the fact that the present study was conducted on healthy men, free from noxious industrial exposure, using state-of-the-art methods, these prediction equations may be regarded as the definitive norms for adult South African males

    Some Variations on Maxwell's Equations

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    In the first sections of this article, we discuss two variations on Maxwell's equations that have been introduced in earlier work--a class of nonlinear Maxwell theories with well-defined Galilean limits (and correspondingly generalized Yang-Mills equations), and a linear modification motivated by the coupling of the electromagnetic potential with a certain nonlinear Schroedinger equation. In the final section, revisiting an old idea of Lorentz, we write Maxwell's equations for a theory in which the electrostatic force of repulsion between like charges differs fundamentally in magnitude from the electrostatic force of attraction between unlike charges. We elaborate on Lorentz' description by means of electric and magnetic field strengths, whose governing equations separate into two fully relativistic Maxwell systems--one describing ordinary electromagnetism, and the other describing a universally attractive or repulsive long-range force. If such a force cannot be ruled out {\it a priori} by known physical principles, its magnitude should be determined or bounded experimentally. Were it to exist, interesting possibilities go beyond Lorentz' early conjecture of a relation to (Newtonian) gravity.Comment: 26 pages, submitted to a volume in preparation to honor Gerard Emch v. 2: discussion revised, factors of 4\pi corrected in some equation

    Integrated Focal Plane Arrays for Millimeter-wave Astronomy

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    We are developing focal plane arrays of bolometric detectors for sub-millimeter and millimeter-wave astrophysics. We propose a flexible array architecture using arrays of slot antennae coupled via low-loss superconducting Nb transmission line to microstrip filters and antenna-coupled bolometers. By combining imaging and filtering functions with transmission line, we are able to realize unique structures such as a multi-band polarimeter and a planar, dispersive spectrometer. Micro-strip bolometers have significantly smaller active volume than standard detectors with extended absorbers, and can realize higher sensitivity and speed of response. The integrated array has natural immunity to stray radiation or spectral leaks, and minimizes the suspended mass operating at 0.1 - 0.3 K. We also discuss future space-borne spectroscopy and polarimetry applications

    On the virial coefficients of nonabelian anyons

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    We study a system of nonabelian anyons in the lowest Landau level of a strong magnetic field. Using diagrammatic techniques, we prove that the virial coefficients do not depend on the statistics parameter. This is true for all representations of all nonabelian groups for the statistics of the particles and relies solely on the fact that the effective statistical interaction is a traceless operator.Comment: 9 pages, 3 eps figure

    Vector coherent state representations, induced representations, and geometric quantization: II. Vector coherent state representations

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    It is shown here and in the preceeding paper (quant-ph/0201129) that vector coherent state theory, the theory of induced representations, and geometric quantization provide alternative but equivalent quantizations of an algebraic model. The relationships are useful because some constructions are simpler and more natural from one perspective than another. More importantly, each approach suggests ways of generalizing its counterparts. In this paper, we focus on the construction of quantum models for algebraic systems with intrinsic degrees of freedom. Semi-classical partial quantizations, for which only the intrinsic degrees of freedom are quantized, arise naturally out of this construction. The quantization of the SU(3) and rigid rotor models are considered as examples.Comment: 31 pages, part 2 of two papers, published versio
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