Imaging delocalized electron clouds: photoionization of C(60) in Fourier reciprocal space

The dynamics of the photoionization of the two outermost orbitals of C(60) has been studied in the oscillatory regime from threshold to the carbon K edge. We show that geometrical properties of the fullerene electronic hull, such as its diameter and thickness, are contained in the partial photoionization cross sections by examining ratios of partial cross sections as a function of the photon wave number in the Fourier conjugated space. Evaluated in this unconventional manner photoemission data reveal directly the desired spatial information.     

Quantum Field Theory on a Discrete Space and Noncommutative Geometry

We analyze in detail the quantization of a simple noncommutative model of spontaneous symmetry breaking in zero dimensions taking into account the noncommutative setting seriously. The connection to the counting argument of Feynman diagrams of the corresponding theory in four dimensions is worked out explicitly. Special emphasis is put on the motivation as well as the presentation of some well-known basic notions of quantum field theory which in the zero-dimensional theory can be studied without being spoiled by technical complications due to the absence of divergencies.     

Application of centrifugal vacuum concentrators in residue analysis

Summary Centrifugal vacuum concentrators can be applied in residue analysis successfully: They prevent the samples from bumping and foaming. Even methanol/water- or acetonitrile/water-mixtures as extracts from food or other samples can be concentrated without separation of water prior to the evaporation process. Sulfonamides and other drugs can be concentrated with 100% recovery. Extracts with some light-sensitive substances (nitrofuranes) were evaporated without losses, as well as some hydrolysis-sensitive substances (penicillins) solved in water, whereas tetracyclines decompose in aqueous solution considerably. For more volatile substances (such as organochlorine pesticides or polychlorinated biphenyls) centrifugal vacuum concentrators can be used for preconcentration e.g. of the gelchromatographic eluate. Further, centrifugal vacuum concentrators can automate the evaporation process. In comparison to rotary evaporators, they save time for the laboratory staff when running series of 4 or more samples. It is very important to supply permanently sufficient energy for the evaporation process, especially when concentrating volumes of 10 ml or more. If the only heated part is the wall of the centrifuge, after couple of minutes the samples cool down to very low temperatures, and the evaporation process slows down. A more efficient way to supply evaporation energy is by means of IR radiation. A very modern device offers an electronically controlled IR radiation by means of temperature control on the centrifugal tubes. This in combination with vapour pressure control ensures an optimal control of the most important factors of the evaporation process.     

Quadratic assignment problems

This paper surveys quadratic assignment problems (QAP). At first several applications of this problem class are described and mathematical formulations of QAPs are given. Then some exact solution methods and good heuristics are outlined. Their computational behaviour is illustrated by numerical results. Further recent results on the asymptotic probabilistic behaviour of QAPs are outlined.     

Modular inclusion,the Hawking temperature,and quantum field theory in curved spacetime

A recent result by Borchers connecting geometric modular action, modular inclusion and spectrum condition, is applied in quantum field theory on spacetimes with a bifurcate Killing horizon (these are generalizations of black-hole spacetimes, comprising the familiar black-hole spacetime models). Within this framework, we give sufficient, model-independent conditions ensuring that the temperature of thermal equilibrium quantum states is the Hawking temperature.     

The imaginary part of the nucleon-nucleus optical potential in semiclassical approximation

We calculate in a novel Thomas-Fermi theory for multiparticle-multihole states the contributions of the correlation and polarization graphs to the imaginary part of the nucleon-nucleus optical potential $\text{W(ω,}\text{R}\text{,}\text{P}\text{)}$ depending on energy, radius and momentum. The present theory generalizes the older Fermi-gas and local-density approximations to this problem in the sense that we can assess precisely the validity of our approach. We show that it yields results which coincide with the average part of a corresponding quantal calculation. We use a gaussian finite-range effective interaction derived from the Gogny force and phenomenological mean-field potentials of the Woods-Saxon or harmonic-oscillator type. With these ingredients and no further adjustable parameters our results for the depth and volume integrals are in good agreement with the average trend of the elastic scattering data. Further, the resulting momentum dependence of W is strong, especially for small P. The influence of the Pauli principle is studied in detail.     

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.