Klaus Morawetz

Adsorption of PTCDA on a partially KBr covered Ag(111) substrate

Ordered growth of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) on Ag(111) partially covered by one or two monolayers of KBr was investigated by non-contact AFM with molecular resolution. Different adsorption patterns are found on the pure substrate, the one covered by a single monolayer, and the one covered by two monolayers KBr. Simulations with an extended Ising-type model reproduce these experimental patterns very well. The adsorbate-adsorbate and the adsorbate-substrate interaction parameters obtained from the simulation are discussed with respect to the interactions at the Ag(111)|KBr interface. As a result, alkali halide covered metals can be used for tuning the interactions and designing adsorption systems, which opens up new possibilities in the control of self-assembled nanostructures.

Kinetic equation for strongly interacting dense fermi systems.

We review the non-relativistic Greens-function approach to the kinetic equations for Fermi liquids far from equilibrium. The emphasis is on the consistent treatment of the off-shell motion between collisions and on the non-instant and non-local picture of binary collisions.
The resulting kinetic equation is of the Boltzmann type, and it represents an interpolation between the theory of transport in metals and the theory of moderately dense gases. The free motion of particles is renormalised by various mean field and mass corrections in the spirit of Landaus quasiparticles in metals. The collisions are non-local in the spirit of Enskogs theory of non-ideal gases. The collisions are moreover non-instant, a feature which is absent in the theory of gases, but which is shown to be important for dense Fermi systems.
In spite of its formal complexity, the presented theory has a simple implementation within the Monte-Carlo simulation schemes. Applications in nuclear physics are given for heavy-ion reactions and the results are compared with the former theory and recent experimental data.
The effect of the off-shell motion and the non-local and non-instant collisions on the dynamics of the system can be characterised in terms of thermodynamic functions such as the energy density or the pressure tensor. Non-equilibrium counterparts of these functions and the corresponding balance equations are derived and discussed from two points of view. Firstly, they are used to prove the conservation laws. Secondly, the role of individual microscopic mechanisms in fluxes of particles and momenta and in transformations of the energy is clarified.

NONLOCAL CORRECTIONS TO THE BOLTZMANN EQUATION FOR DENSE FERMI SYSTEMS

Abstract A kinetic equation which combines the quasiparticle drift of Landaus equation with a dissipation governed by a nonlocal and noninstant scattering integral in the spirit of Sniders equation for gases is derived. Consequent balance equations for the density, momentum and energy include quasiparticle contributions and the second-order quantum virial corrections. The medium effects on binary collisions are shown to mediate the latent heat, i.e. an energy conversion between correlation and thermal energy. An implementation to heavy ion collisions is discussed.A kinetic equation which combines the quasiparticle drift of Landaus equation with a dissipation governed by a nonlocal and noninstant scattering integral in the spirit of Sniders equation for gases is derived. Consequent balance equations for the density, momentum and energy include quasiparticle contributions and the second order quantum virial corrections. The medium effects on binary collisions are shown to mediate the latent heat, i.e., an energy conversion between correlation and thermal energy. An implementation to heavy ion collisions is discussed.

Short-time dynamics with initial correlations

The short-time dynamics of correlated systems is strongly influenced by initial correlations, giving rise to an additional collision integral in the non-Markovian kinetic equation. Exact cancellation of the two integrals is found if the initial state is thermal equilibrium, which is an important consistency criterion. Analytical results are given for the time evolution of the correlation energy, which are confirmed by comparisons with molecular dynamics simulations.

Virial Corrections to Simulations of Heavy Ion Reactions

Within quantum molecular dynamics (QMD) simulations we demonstrate the effect of virial corrections on heavy ion reactions. Unlike in standard codes, the binary collisions are treated as nonlocal so that the contribution of the collision flux to the reaction dynamics is covered. A comparison with standard QMD simulations shows that the virial corrections lead to a broader proton distribution bringing theoretical spectra closer towards experimental values. Complementary Boltzmann-Uehling-Uhlenbeck simulations reveal that the nonlocality enhances the collision rate in the early stage of the reaction. It suggests that the broader distribution appears due to an enhanced preequilibrium emission of particles. [S0031-9007(99)09104-8] The Boltzmann equation including the Pauli blocking [the Boltzmann-Uehling-Uhlenbeck (BUU) equation [1]] and the closely related method of quantum molecular dynamics (QMD) [2,3] are extensively used to interpret experimental data from heavy ion reactions. Because of their quasiclassical character, they offer a transparent picture of the internal dynamics of reactions and allow one to link observed particle spectra with individual stages of reactions. The expectation to cover the heavy ion reactions within experimental errors has been recently set back by a failure of BUU simulations to describe the energy and angular distribution of neutrons and protons in the energy domain #200 MeVyA [4‐6]. Indeed, the Boltzmann equation does not contain all of the relevant physics. As noticed in numerical studies of hard sphere cascades by Halbert [7] and, more generally, by Malfliet [8], it is unfortunate that all dynamical models rely more or less on the use of the space- and time-local approximation of binary collisions inherited from the Boltzmann equation. This approximation neglects a contribution of the collision flux to the compressibility and the shear viscosity which control the hydrodynamic motion during the reaction. In order to include the collision flux and other virial corrections, the nonlocal character of binary collisions has to be accounted for. Malfliet also demonstrated that nonlocal collisions can be easily incorporated into BUU simulation codes.

Theory of water and charged liquid bridges

The phenomenon of liquid bridge formation due to an applied electric field is investigated. A solution of a charged catenary is presented, which allows one to determine the static and dynamical stability conditions where charged liquid bridges are possible. The creeping height, the bridge radius and length, as well as the shape of the bridge are calculated showing an asymmetric profile, in agreement with observations. The flow profile is calculated from the Navier-Stokes equation leading to a mean velocity, which combines charge transport with neutral mass flow and which describes recent experiments on water bridges.

Nonlinear theory of deformable superconductors: Ginzburg-Landau description

Pavel Lipavský, Klaus Morawetz, Jan Koláček and Ernst Helmut Brandt 1 Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 12116 Prague 2, Czech Republic Institute of Physics, Academy of Sciences, Cukrovarnická 10, 16253 Prague 6, Czech Republic Forschungszentrum Rossendorf, PF 51 01 19, 01314 Dresden, Germany Max-Planck-Institute for the Physics of Complex Systems, Noethnitzer Str. 38, 01187 Dresden, Germany and Max-Planck-Institute for Metals Research, D-70506 Stuttgart, Germany

Correlations in Many-Body Systems with Two-time Green's Functions

Max-Planck-Institute for the Physics of Complex Systems, Noethnitzer Str. 38, 01187 Dresden, Germany(February 8, 2008)The Kadanoff-Baym (KB) equations are solved numerically for infinite nuclear matter. In particularwe calculate correlation energies and correlation times. Approximating the Green’s functions in theKB collision kernel by the free Green’s functions the Levinson equation is obtained. This approxi-mation is valid for weak interactions and/or low densities. It relates to the extended quasi-classicalapproximation for the spectral function. Comparing the Levinson, Born and KB calculations allowsfor an estimate of higher order spectral corrections to the correlations. A decrease in binding energyis reported due to spectral correlations and off-shell parts in the reduced density matrix.I. INTRODUCTION

QUASIPARTICLE TRANSPORT EQUATION WITH COLLISION DELAY. II. MICROSCOPIC THEORY

For a system of noninteracting electrons scattered by neutral impurities, we derive a modified Boltzmann equation that includes quasiparticle and virial corrections. We start from a quasiclassical transport equation for nonequilibrium Green`s functions and apply a limit of small scattering rates. The resulting transport equation for quasiparticles has gradient corrections to scattering integrals. These gradient corrections are rearranged into a form characteristic for virial corrections. {copyright} {ital 1997} {ital The American Physical Society}

NONINSTANTANEOUS COLLISIONS AND TWO CONCEPTS OF QUASIPARTICLES

The kinetic theory recently implemented in heavy ion reactions combines a non-local and non-instant picture of binary collisions with quasiparticle features. We show that the non-instant description is compatible with the spectral concept of quasiparticles while the commonly used variational concept is consistent only with instant collisions. The rearrangement energy, by which the variational concept surpasses the spectral one, is shown to be covered by a medium effect on non-instant collisions.