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  • 24.10.Cn  (5)
  • 25.70.−z  (4)
  • 11.30.Qc  (1)
Materialart
Erscheinungszeitraum
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 331 (1988), S. 439-449 
    ISSN: 1434-601X
    Schlagwort(e): 24.10.Cn ; 24.10.-i
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We derive a transport equation for the description of non-relativistic heavy-ion collisions from time-dependentG-matrix theory. The approximations introduced are investigated within a modified Lipkin model on theA-body level and by one-dimensional calculations for colliding finite fermion systems on the two-body level. Both approximations are found to hold reasonably well. The classical limit of these equations in phase space yields a transport equation of the Vlasov-Uehling-Uhlenbeck type without double counting of interactions and uniquely determines the time-dependent mean field as well as an in-medium nucleon-nucleon cross-section on the basis of the sameG-matrix.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 353 (1995), S. 301-310 
    ISSN: 1434-601X
    Schlagwort(e): 11.30.Qc ; 11.90.+t
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Using the cluster expansions for n-point Green functions we derive a closed set of dynamical equations of motion for connected equal-time Green functions by neglecting all connected functions higher than 4 th order for theλΦ 4-theory in 1 + 1 dimensions. We apply the equations to the investigation of spontaneous symmetry breaking, i.e. to the evaluation of the effective potential at temperatureT=0. Within our momentum space discretization we obtain a second order phase transition (in agreement with the Simon-Griffith theorem) and a critical coupling ofλ crit /4m 2=2.446 as compared to a first order phase transition andλ crit /4m 2=2.568 from the Gaussian effective potential approach.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 342 (1992), S. 161-167 
    ISSN: 1434-601X
    Schlagwort(e): 24.10.Cn ; 25.70.−z
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present a coupled set of equations for the one-body density matrix and the two-body correlation function consistent with trace relations and conservation laws which provide an extension of correlation dynamics on the two-body level. The additional interaction terms are discussed in the context of time-dependent G-matrix theory and NQCD and studied numerically by one-dimensional calculations for colliding finite fermion systems.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 337 (1990), S. 1-10 
    ISSN: 1434-601X
    Schlagwort(e): 05.60.+w ; 11.10.Qr ; 24.10.Cn ; 25.70.-z
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We present an extension of relativistic mean-field theories within the framework of quantum correlation dynamics starting from an effective hadronic Lagrangian density with minimal coupling between baryons and mesons. When neglecting retardation for the meson fields the conventional meson-exchange picture is obtained for the baryon-baryon interaction. The resulting equations of motion for the baryonic one-body density matrix and two-body correlation spinor matrix provide a nonperturbative framework for the description of relativistic heavy-ion collisions. Adopting semiclassical limits for the Wigner transform of the one-body density matrix a covariant transport equation is derived in the limit of time-dependent Dirac-Brueckner theory. It describes the mean-field dynamics including momentum-dependent potentials as well as in-medium nucleon-nucleon collisions on the basis of the same meson fields without double counting of interactions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 337 (1990), S. 175-183 
    ISSN: 1434-601X
    Schlagwort(e): 24.10.Cn ; 25.70.−z
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamical description of strongly interacting finite Fermi systems is based on coupled equations of motion for the one-body density matrixρ(11′) and the two-body correlation functionc 2(12, 1′2′) as obtained from the density-matrix hierarchy. The truncation schemes considered exceed the conventional Brueckner-Hartree-Fock scheme and also apply for nonstationary problems. In the limit of slow processes in time the equation of motion for the two-body correlation functionc 2 can be integrated in time and closed expressions can be given for the dynamical evolution ofρ(11′). When performing a Wigner transformation and adopting semiclassical limits this gives a transport equation of the Uehling-Uhlenbeck type for the one-body phase-space distributionf(x,p;t). Furthermore, in the small amplitude limit, we obtain a set of coupled equations for particle-hole (p-h),2p-2p, 2h-2h, 2p-2h, 1p-3h, 1h-3p amplitudes beyond the level of second RPA which provide a genuine basis for the description of giant resonances and their damping width.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 340 (1991), S. 287-295 
    ISSN: 1434-601X
    Schlagwort(e): 25.70.−z ; 25.70.Np
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Within a covariant BUU-approach we simulate heavyion collisions at various bombarding energies from 400 MeV/u to 1 GeV/u. We evaluate locally the energymomentum tensorT μv (x), and extract pressures, energydensities and temperatures. The connection of these thermodynamical quantities to experimental observables and their sensitivity to the equation of state is discussed. Furthermore, we investigate the question of local equilibration and evaluate the entropy produced in these reactions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 326 (1987), S. 21-31 
    ISSN: 1434-601X
    Schlagwort(e): 25.70.−z ; 25.70.Lm
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A one-dimensional toy model of two moving finite boxes is analysed with respect to quantal phenomena associated with heavy-ion dynamics at low and intermediate energies. Special attention is payed to the relation between energy and momentum of the nucleons inside and outside the time-dependent mean field. A Wigner transformation of the one-body density matrix in space and time allows for a unique comparison with classical phase-space dynamics. It is found that high momentum components of the nuclear groundstate wave function approximately become on-shell during the heavy-ion reaction. This leads to the emission of energetic nucleons which do not appear classically. It is furthermore shown, that the low lying eigenstates of the dinuclear system for fixed time are only partly occupied throughout the reaction at intermediate energies. This opens up final phase space for nucleons after producing e.g. a pion or energetic photon. Though the present model does not allow for a reliable calculation of double differential nucleon spectra, pion or photon cross sections, it transparently shows the peculiar features of quantum dynamics in heavy-ion collisions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 328 (1987), S. 423-429 
    ISSN: 1434-601X
    Schlagwort(e): 24.10.Cn ; 24.10.−i
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A selfconsistent quantal two-body theory as obtained from the density-matrix hierarchy is solved numerically for the first time for a one-dimensional system modelling α+ α collisions at 80 MeV/u. Various truncation schemes for the two-body correlation function are investigated in order to explore the convergence properties of the theory. We find that perturbative treatments with respect to two-body processes do not yield reliable results in the energy regime investigated and that the nuclear stopping power sensitively depends on the order of the two-body correlations considered.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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