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Creators/Authors contains: "Allen, T.J."
  1. We consider the effects of going beyond the approximation of a straight string in mesons by using a flexible flux tube model wherein a Nambu-Goto string bends in response to quark accelerations. The curved string is dynamically identical to the straight string even for ultra-relativistic mesons except for a small additional radial momentum. We numerically solve the curved string model in the case where both ends have equal mass quarks and also in the case where one end is fixed. No approximation of non-relativistic motion is made. We note some small but interesting differences from the straight string. {copyright} {italmore » 1999} {ital The American Physical Society}« less
  2. It is well known that a straight Nambu-Goto string is an exact solution of the equations of motion when its end moves in a circular orbit. In this paper we investigate the shape of a confining relativistic string for a general motion of its end. We determine analytically the shape of the curved string to leading order in deviation from straightness, and show that it reduces to an expected non-relativistic result. We also demonstrate numerically that in realistic meson models this deviation is always small. We further find that the angular momentum and energy are the same as for themore » straight string, but that the curved string has a small radial momentum not present in a straight string. Our results justify the common assumption of straight strings usually made in hadron models. {copyright} {ital 1999} {ital The American Physical Society}« less
  3. BEDT-TTF based organic metals with tetrahedral and linear anions are reviewed. New (ET){sub 2}MX{sub 4} complexes, their electrical and ESR properties are reported (M = Ga, In, Tl, and X is halides). A novel solid state phase transformation from semiconducting {alpha} to superconducting {beta}-(ET){sub 2}IBr{sub 2} is presented.
  4. In this communication the authors compare the carbonate, citrate, and oxalate solution techniques for the synthesis of the high-T/sub c/ compounds La/sub 2-x/Sr/sub x/CuO/sub 4/. The superconducting properties of the compounds are determined as much by the oxygen stoichiometry as by the metal stoichiometry, and therefore, the sintering and annealing temperatures and O/sub 2/ partial pressures all influence the conductive properties of the materials.
  5. Single crystals in the La-Ba-Cu-O system (LBCO) have been prepared, and x-ray structural characterization and superconducting properties of the crystals are reported. The superconductivity of the sample was detected by rf penetration depth measurements at 500 kHz. The onset temperature for the superconductivity (Tc) was 8.5 - 9.0 K with a broad transition and a low signal response. These findings indicate that only a small fraction of the sample had bulk superconductivity, and the crystals possess a range of Tc values. 13 references, 1 figure, 1 table.
  6. BEDT-TTF based organic metals with tetrahedral and linear anions are reviewed. New (ET)/sub 2/MX/sub 4/ complexes, their electrical and ESR properties are reported (M = Ga, In, Tl, and X is halides). A novel solid state phase transformation from semiconducting ..cap alpha.. to superconducting ..beta..-(ET)/sub 2/IBr/sub 2/ is presented. 40 refs., 5 figs., 2 tabs.
  7. The authors of this paper derive explicit forms for the neutrino and lepton mixing-matrices which describe the generic singular see-saw model. The dependence on the hierarchy parameter is contrasted with the non-singular case. Application is made to Simpson's 17 keV neutrino.
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