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  • 1985-1989  (2)
  • 1970-1974
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  • 1910-1914
  • 07.77  (1)
  • 58G11  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 43 (1987), S. 247-255 
    ISSN: 1432-0630
    Keywords: 78.70BJ ; 07.77
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Low-energy intense positron beams derived from pair production can be made at high-energy electron linacs and such beams are in operation or under installation at several linac facilities. Using a pulsed position beam made at a 100 MeV electron linac, we have measured the intensity and velocity distribution of positronium emitted from materials by measuring the time-of-flight of annihilating positronium. The time-of-flight data are augmented by positron lifetime and angular correlation measurements performed with the beam. Positronium spectra have been measured for a number of metallic samples. Several new observations have been made including details of the energy distribution of positronium emission formed by a thermalized positron and a conduction electron and the production of positronium from energetic positrons scattered out of the sample.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Acta applicandae mathematicae 12 (1988), S. 1-33 
    ISSN: 1572-9036
    Keywords: 58G11 ; 58G32 ; 60H15 ; Bochner's theorem ; Brownian motion and heat flow ; spectrum of the Laplacian ; hyperbolic manifolds ; cohomology with compact support
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Bochner's theorem that a compact Riemannian manifold with positive Ricci curvature has vanishing first cohomology group has various extensions to complete noncompact manifolds with Ricci possibly negative. One still has a vanishing theorem for L 2 harmonic one-forms if the infimum of the spectrum of the Laplacian on functions is greater than minus the infimum of the Ricci curvature. This result and its analogues for p-forms yield vanishing results for certain infinite volume hyperbolic manifolds. This spectral condition also imposes topological restrictions on the ends of the manifold. More refined results are obtained by taking a certain Brownian motion average of the Ricci curvature; if this average is positive, one has a vanishing theorem for the first cohomology group with compact supports on the universal cover of a compact manifold. There are corresponding results for L 2 harmonic spinors on spin manifolds.
    Type of Medium: Electronic Resource
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