87 research outputs found

    Reversed Currents in Charged Liquid Bridges

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    The velocity profile in a water bridge is reanalyzed. Assuming hypothetically that the bulk charge has a radial distribution, a surface potential is formed that is analogous to the Zeta potential. The Navier Stokes equation is solved, neglecting the convective term; then, analytically and for special field and potential ranges, a sign change of the total mass flow is reported caused by the radial charge distribution

    Quasiparticle parameterization of meanfields, Galilei invariance and universal conserving response functions

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    The general possible form of meanfield parameterization in a running frame in terms of current, energy and density functionals are examined under the restrictions of Galilean invariance. It is found that only two density-dependent parameters remain which are usually condensed in a position-dependent effective mass and the selfenergy formed by current and mass. The position-dependent mass induces a position-dependent local current which is identified for different nonlinear frames. In a second step the response to an external perturbation and relaxation towards a local equilibrium is investigated. The response function is found to be universal in the sense that the actual parameterization of the local equilibrium does not matter and is eliminated from the theory due to the conservation laws. The explicit form of the response with respect to density, momentum and energy is derived. The compressibility sum rule as well as the sum rule by first and third-order frequency moments are proved analytically to be fulfilled simultaneously. The results are presented for Bose- or Fermi systems in one- two and three dimensions.Comment: Phys Rev E in pres

    Dynamical constraints on phase transitions

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    The numerical solutions of nonlocal and local Boltzmann kinetic equations for the simulation of central heavy ion reactions are parameterized in terms of time dependent thermodynamical variables in the Fermi liquid sense. This allows one to discuss dynamical trajectories in phase space. The nonequilibrium state is characterized by non-isobaric, non-isochoric etc. conditions, shortly called iso-nothing conditions. Therefore a combination of thermodynamical observables is constructed which allows one to locate instabilities and points of possible phase transition in a dynamical sense. We find two different mechanisms of instability, a short time surface - dominated instability and later a spinodal - dominated volume instability. The latter one occurs only if the incident energies do not exceed significantly the Fermi energy and might be attributed to spinodal decomposition. In contrast the fast surface explosion occurs far outside the spinodal region and pertains also in the cases where the system develops too fast to suffer a spinodal decomposition and where the system approaches equilibrium outside the spinodal region.Comment: language corrections and figure decorations adde

    Quantum response of finite Fermi systems and the relation of Lyapunov exponent to transport coefficients

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    Within the frame of kinetic theory a response function is derived for finite Fermi systems which includes dissipation in relaxation time approximation and a contribution from additional chaotic processes characterized by the largest Lyapunov exponent. A generalized local density approximation is presented including the effect of many particle relaxation and the additional chaotic scattering. For small Lyapunov exponents relative to the product of wave vector and Fermi velocity in the system, the largest Lyapunov exponent modifies the response in the same way as the relaxation time. Therefore the transport coefficients can be connected with the largest positive Lyapunov exponent in the same way as known from the transport theory in relaxation time approximation

    Transport with three-particle interaction

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    Starting from a point - like two - and three - particle interaction the kinetic equation is derived. While the drift term of the kinetic equation turns out to be determined by the known Skyrme mean field the collision integral appears in two - and three - particle parts. The cross section results from the same microscopic footing and is naturally density dependent due to the three - particle force. By this way no hybrid model for drift and cross section is needed for nuclear transport. Besides the mean field correlation energy the resulting equation of state has also a two - and three - particle correlation energy which are both calculated analytically for the ground state. These energies contribute to the equation of state and lead to an occurrence of a maximum at 3 times nuclear density in the total energy.Comment: typos correction

    Critical Tsallis exponent in heavy ion reaction

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    The numerical solution of the nonlocal kinetic equation allows to simulate heavy ion reactions around Fermi energy. The expansion velocity and density profile show specific radial dependence which can be described with a Tsallis exponent of q=5/3q=5/3. This might be considered as an indication of a phase transition.Comment: 4 pages, conference proceedings NEXT200

    Nonequilibrium thermodynamics with binary quantum correlations

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    The balance equations for thermodynamic quantities are derived from the nonlocal quantum kinetic equation. The nonlocal collisions lead to molecular contributions to the observables and currents. The corresponding correlated part of the observables is found to be given by the rate to form a molecule multiplied with its lifetime which can be considered as collision duration. Explicit expressions of these molecular contributions are given in terms of the scattering phase shifts. The two-particle form of the entropy is derived. This extends the Landau quasiparticle picture by two-particle molecular contributions. There is a continuous exchange of correlations into kinetic parts condensing into the rate of correlated variables for energy and momentum. For the entropy, an explicit gain remains and Boltzmann's H-theorem is proved including the molecular parts of the entropy.Comment: corrected formula

    General response function for interacting quantum liquids

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    Linearizing the appropriate kinetic equation we derive general response functions including selfconsistent mean fields or density functionals and collisional dissipative contributions. The latter ones are considered in relaxation time approximation conserving successively different balance equations. The effect of collisions is represented by correlation functions which are possible to calculate with the help of the finite temperature Lindhard RPA expression. The presented results are applicable to finite temperature response of interacting quantum systems if the quasiparticle or mean field energy is parameterized within Skyrme - type of functionals including density, current and energy dependencies which can be considered alternatively as density functionals. By this way we allow to share correlations between density functional and collisional dissipative contributions appropriate for the special treatment. We present results for collective modes like the plasmon in plasma systems and the giant resonance in nuclei. The collisions lead in general to an enhanced damping of collective modes. If the collision frequency is close to the frequency of the collective mode, resonance occurs and the collective mode is enhanced showing a collisional narrowing
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