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Subject: search.filters.subject.530Institute: search.filters.UBSInstitut.Sonstige EinrichtungStart date: 1986End date: 1989Author: search.filters.author.Ertl, ThomasAuthor: search.filters.author.Geyer, Florian

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Now showing 1 - 4 of 4
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    Rydberg atoms in uniform magnetic fields: uncovering the transition from regularity to irregularity in a quantum system
    (1986) Wunner, Günter; Woelk, Ulrich; Zech, Ingrid; Zeller, Gudrun; Ertl, Thomas; Geyer, Florian; Schweizer, Wolfgang; Ruder, Hanns
    We investigate the eigenvalue spectra of hydrogen Rydberg atoms in strong magnetic fields for manifestations of quantum stochasticity and find (i) a smooth transition from a Poisson-type to a Wigner-type distribution of level spacings in the range of energy where classical motion becomes increasingly chaotic, (ii) the occurrence of multiple avoided crossings, and (iii) connected with this, an extreme sensitivity of oscillator strengths, and thus of observable spectra, with respect to small variations of an external parameter, viz., the magnetic field strength.
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    Analysis of hydrogen Rydberg spectra in a uniform magnetic field: uncovering the transition from regularity to irregularity in a real quantum system
    (1986) Wunner, Günter; Woelk, Ulrich; Zech, Ingrid; Zeller, Gudrun; Ertl, Thomas; Geyer, Florian; Steitz, Arno; Schweizer, Wolfgang; Ruder, Hanns
    Studies of the behaviour of quantum systems in a range of energy where their classical counterparts undergo transitions from regularity to irregularity, as manifested in phase space by the gradual destruction of invariant tori, to date have largely been confined to model Hamiltonian systems such as harmonic oscillators with cubic, quartic, or higher-degree polynomial corrections, or the stadium problem. We show that phenomena which have turned out characteristic of the onset of "quantum stochasticity" in these model systems can in fact be recovered in the quantal energy spectra of a "real" physical system, viz. spectra of hydrogen Rydberg atoms in strong magnetic fields. This implies that one has a simple prototype system at hand in which to study - not only in theory but also in experiment, quantitatively and in detail, and as a function of a continuously tunable external parameter - phenomena that are expected to be typical of the quantum properties of nonintegrable systems in general.
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    Line-of-sight integration: a powerful tool for visualization of three-dimensional scalar fields
    (1989) Ruder, Hanns; Ertl, Thomas; Geyer, Florian; Herold, Heinz; Kraus, Ute
    An easy conceivable but very powerful method for the visualization of three-dimensional scalar fields is described. The way this method works is illustrated by some examples and the computed pictures are compared with the results of other methods of representation.
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    Visualization in astrophysics
    (1989) Ertl, Thomas; Geyer, Florian; Herold, Heinz; Kraus, Ute; Niemeier, Roland; Nollert, Hans-Peter; Rebetzky, Andreas; Ruder, Hanns; Zeller, Gudrun
    This paper reports on progress we have made in modelling cosmic X·ray sources on supercomputers. The results we present are meant to serve as an example for the fact that sophisticated visualization techniques play a crucial role in scientific computing. Among the graphical methods we demonstrate, raytracing in curved space-time and a physically motivated 3D-volume rendering algorithm might be of interest to the graphics community in general.