Evolution of ultracold neutral plasmas

We present the first large-scale simulations of an ultracold neutral plasma, produced by photoionization of laser-cooled xenon atoms, from creation to initial expansion, using classical molecular-dynamics methods with open boundary conditions. We reproduce many of the experimental findings such as the trapping efficiency of electrons with increased ion number, a minimum electron temperature achieved on approach to the photoionization threshold, and recombination into Rydberg states of an anomalously low principal quantum number. In addition, many of these effects establish themselves very early in the plasma evolution ( similar ns) before the present experimental observations begin.     

Potentialtheoretische Randwertprobleme bei Tensorfeldern beliebiger Dimension und beliebigen Ranges

Ohne ZusammenfassungHerrn Prof. Dr. Ludwig Biermann zum 65. Geburtstag gewidmet Vorgelegt von H. Görtler Diese Arbeit entstand am Max-Planck-Institut für Physik und Astrophysik, München.     

Control of vertically coupled InGaAs/GaAs quantum dots with electric fields

Controllable interactions that couple quantum dots are a key requirement in the search for scalable solid state implementations for quantum information technology. From optical studies of excitons and corresponding calculations, we demonstrate that an electric field on vertically coupled pairs of In(0.6)Ga(0.4)As/GaAs quantum dots controls the mixing of the exciton states on the two dots and also provides controllable coupling between carriers in the dots.     

Nuclear stopping from 0.09A to 1.93A GeV and its correlation to flow

We present a complete systematics (excitation functions and system-size dependences) of global stopping and side flow for heavy ion reactions in the energy range between 0.09A and 1.93A GeV. For the heaviest system, Au+Au, we observe a plateau of maximal stopping extending from about 0.2A to 0.8A GeV with a fast drop on both sides. The degree of stopping, which is shown to remain significantly below the expectations of a full stopping scenario, is found to be highly correlated to the amount of side flow.     

On the low wave number asymtotics for the two-dimensional exterior dirichlet problem for the reduced wave equation

A new proof is given for the low wave number asymptotics for the solutions to the exterior Dirichlet problem for the reduced wave equation in two dimensions.     

Numerical treatment of retarded boundary integral equations by sparse panel clustering

Stefan Sauter Institute for Mathematics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland ^{We consider the wave equation in a boundary integral formulation.The discretization in time is done by using convolution quadraturetechniques and a Galerkin boundary element method for the spatialdiscretization. In a previous paper, we have introduced a sparseapproximation of the system matrix by cut-off, in order to reducethe storage costs. In this paper, we extend this approach byintroducing a panel clustering method to further reduce thesecosts.}     

Electric field control of exciton states in quantum dot molecules

Semiconductor nanostructures have attracted considerable interest during the recent years in view of the potential application in quantum information processing. In particular, quantum dots have been suggested to fulfill an essential requirement for quantum computation: controllable interaction that couples two quantum dot qubits. Previous experiments on two vertically aligned quantum dots have demonstrated the formation of coupled exciton states. We show that this coupling between two In_0.60Ga_0.40As/GaAs quantum dots can be tuned by an electric field applied along the molecule axis. This controllable coupling in such a relatively simple configuration could be implemented in a solid-state-based quantum device.     

Ein kombiniertes Dirichlet-Neumannsches Randwertproblem bei harmonischen Vektorfeldern

Ohne Zusammenfassung Vorgelegt von J. C. C. Nitsche     

On the Fredholm alternative

We give a proof of the Fredholm alternative for compact operators being adjoint with respect to a nondegenerate bilinear form which is not necessarily bounded.     

Studies on the bromination of pyrimidine. A facile synthesis of 5-bromopyrimidine

Three methods for hromination of pyrimidine were investigated: ( a ) the bromination of pyrimidine hydrochloride in aromatic solvents, ( b ) the vapor phase bromination of pyrimidine, and ( c ) the pyrolysis of pyrimidine hydrochloride perbromide. The addition of bromine to a slurry of pyrimidine hydrochloride in nitrobenzene proved to be superior and afforded excellent yields of 5-bromopyrimidine.