Quantum fluctuations and dynamical chaos: An effective potential approach

We discuss the intimate connection between the chaotic dynamics of a classical field theory and the instability of the one-loop effective action of the associated quantum field theory. Using the example of massless scalar electrodynamics, we show how the radiatively induced spontaneous symmetry breaking stabilizes the vacuum state against chaos, and we speculate that monopole condensation can have the same effect in non-Abelian gauge theories.     

Time structure and atomic excltation spectra in heavy-ion collisions with nuclear contact

From a quantum mechanical model for quasielastic nuclear scattering, employing a pocket in the internuclear potential at close distances, a distribution of nuclear delay times is derived. The influence of this time structure on atomic excitation spectra is demonstrated using positron emission from supercritical collisions as an example. In a narrow regime of beam energies close to the Coulomb barrier, a considerable probability for collisions with long nuclear delay times is found, associated with a sharp peak in the positron spectrum which is due to enhanced spontaneous positron production. It is pointed out that quasielastic nuclear scattering alone cannot account for the absolute numbers of spontaneous positrons as extracted from recent experiments. A possible generalization of the theory to include inelastic nuclear processes is briefly discussed.     

Ramanujan's Singular Moduli

In his first notebook, in scattered places, Ramanujan recorded without proofs the values of over 100 class invariants and over 30 singular moduli. This paper is devoted to establishing all of Ramanujan's representations for singular moduli. For those of odd index, new algorithms needed to be developed.     

Pion bremsstrahlung and critical phenomena in relativistic nuclear collisions

We investigate the dependence of pion bremsstrahlung on the deceleration of the nuclei in relativistic heavy ion collisions. The vicinity of an abnormal phase in nuclear matter can lead - owing to critical N-N scattering - to faster deceleration or decreasing transparency of the nuclei. This would result in a threshold enhancement of the pion bremsstrahlung cross section, which in turn can be used to search for abnormal nuclear states experimentally.     

High pressure nebulization: a new way of sample introduction for atomic spectroscopy

Summary The solution to be investigated is nebulized by a pressure of 50 to 400 bar. The liquid sample (5 l to 2 ml) to be analyzed is fed into a sample loop — as is common procedure in HPLC techniques. But instead of being pressed through HPLC columns, the liquid is now pressed through a special nozzle with an opening of a few micrometers. An aerosol results which is then submitted to a spectroscopical source (flame-AAS; ICP/OES). The aerosol yield is more than 50%; even a saturated solution of cooking salt can be nebulized. The sensitivity of flame-AAS increases by about one order of magnitude (signal area). In addition, an effective on-line coupling of HPLC and atomic spectrometric determination methods is possible.

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Hochdruck-ZerstÄubung: eine neue Art der Probeeinführung für die Atomspektroskopie

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Dedicated to Prof. Dr. W. Fresenius on the occasion of his 75th birthday     

Almost complex curves and Hopf hypersurfaces in the nearly Kähler 6-sphere

We characterize Hopf hypersurfaces inS ⁶ as open parts of geodesic hyperspheres or of tubes around almost complex curves ofS ⁶.