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  • Electronic Resource  (4)
  • 2000-2004  (4)
  • 1985-1989
  • 1880-1889
  • 1870-1879
  • 2003  (4)
  • PACS. 64.70.Pf Glass transitions – 78.35.+c Brillouin and Rayleigh scattering; other light scattering – 61.25.Em Molecular liquids  (2)
  • PACS. 75.10.Jm Quantized spin models  (2)
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  • Electronic Resource  (4)
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  • 2000-2004  (4)
  • 1985-1989
  • 1880-1889
  • 1870-1879
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    The extended spin ladder and net models: exact dimer ground state and quantum phase transition (2003)
    Springer
    The European physical journal 31 (2003), S. 63-67 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We investigate an extended spin ladder with diagonal frustrated exchanges in a wide parameter regime. By representing the model as a sum of semidefinite positive projection operators, we prove that this model has exactly a dimer ground state. Smoothly changing parameters may lead the model cover several exactly known models. Starting from this ladder model, we proposed two two-dimensional net models with exact ground states. The quantum phase transition of the ground state, due to the change of exchange strengths along perpendicular rungs, is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00009-7
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Excitations of anisotropic spin-1 chains with matrix product ground state (2003)
    Springer
    The European physical journal 31 (2003), S. 209-216 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 75.10.Jm Quantized spin models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We investigate a large class of antiferromagnetic spin-1 chains with nearest neighbour interaction and exactly known matrix product ground state. The spectrum of low-lying excitations is calculated numerically by DMRG and exact diagonalisation. Spin liquid behaviour with an excitation gap is observed meeting the Haldane scenario. Further, we compare properties of the anisotropic model with the well-known isotropic AKLT model and use the analytical single mode approximation to obtain a quantitative understanding of the excitation gap. The low-lying excited states can be interpreted in terms of a magnon-like elementary excitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00025-7
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Light scattering by longitudinal acoustic modes in supercooled molecular liquids II: microscopic derivation of the phenomenological equations (2003)
    Springer
    The European physical journal 31 (2003), S. 229-246 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 64.70.Pf Glass transitions – 78.35.+c Brillouin and Rayleigh scattering; other light scattering – 61.25.Em Molecular liquids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The constitutive equations for the orientational dynamics of a liquid formed of linear molecules are derived microscopically. The resulting generalised Langevin equations coincide with the phenomenological approach of Dreyfus et al. [1]. Formally exact expressions are given for the phenomenological coefficients and various constraints are shown to be consequences of this microscopic approach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00027-5
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Light scattering by longitudinal acoustic modes in molecular supercooled liquids I: phenomenological approach (2003)
    Springer
    The European physical journal 31 (2003), S. 217-228 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 64.70.Pf Glass transitions – 78.35.+c Brillouin and Rayleigh scattering; other light scattering – 61.25.Em Molecular liquids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We derive expressions for the intensity of the Brillouin polarized spectrum of a molecular liquid formed of axially symmetric molecules. These expressions take into account both the molecular dielectric anisotropy and the modulation of the local polarisability by density fluctuations. They also incorporate all the retardation effects which occur in such liquids. We show that the spectrum splits into a q-independent rotational contribution and q-dependent term, which reflects the propagation of longitudinal acoustic modes. In the latter, the two light scattering mechanisms enter on an equal footing and generate three scattering channels. We study the influence of the two new channels and show that they may substantially modify the Brillouin line-shape when the relaxation time of the supercooled liquid and the period of the acoustic excitation are of the same order of magnitude.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00026-6
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    Paper (German National Licenses)
    Fulltext
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