87 research outputs found
Reversed Currents in Charged Liquid Bridges
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
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
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
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
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
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 . This might be considered as an indication of a phase
transition.Comment: 4 pages, conference proceedings NEXT200
Nonequilibrium thermodynamics with binary quantum correlations
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
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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