Status of the OPERA Experiment

In this article the physics motivation and the detector design of the OPERA experiment will be reviewed. The construction status of the detector, which will be situated in the CNGS beam from CERN to the Gran Sasso laboratory, will be reported. A survey on the physics performance will be given and the physics plan in 2006 will be presented.Comment: 5 pages, 4 figures, conference proceedings, to be published in Acta Physica polonica

Optical absorption in quantum dots: Coupling to longitudinal optical phonons treated exactly

Optical transitions in a semiconductor quantum dot are theoretically investigated, with emphasis on the coupling to longitudinal optical phonons, and including excitonic effects. When limiting to a finite number of $m$ electron and $n$ hole levels in the dot, the model can be solved exactly within numerical accuracy. Crucial for this to work is the absence of dispersion of the phonons. A suitable orthogonalization procedure leaves only $m(m+1)/2+n(n+1)/2-2$ phonon modes to be coupled to the electronic system. We calculate the linear optical polarization following a delta pulse excitation, and by a subsequent Fourier transformation the resulting optical absorption. This strict result is compared with a frequently used approximation modeling the absorption as a convolution between spectral functions of electron and hole, which tends to overestimate the effect of the phonon coupling. Numerical results are given for two electron and three hole states in a quantum dot made from the polar material CdSe. Parameter values are chosen such that a quantum dot with a resonant sublevel distance can be compared with a nonresonant one.Comment: 12 pages, 6 figure

Dephasing in Quantum Dots: Quadratic Coupling to Acoustic Phonons

A microscopic theory of optical transitions in quantum dots with carrier-phonon interaction is developed. Virtual transitions into higher confined states with acoustic phonon assistance add a quadratic phonon coupling to the standard linear one, thus extending the independent Boson model. Summing infinitely many diagrams in the cumulant, a numerically exact solution for the interband polarization is found. Its full time dependence and the absorption lineshape of the quantum dot are calculated. It is the quadratic interaction which gives rise to a temperature-dependent broadening of the zero-phonon line, being here calculated for the first time in a consistent scheme.Comment: 4 pages, 2 figure

Near-field spectra of quantum well excitons with non-Markovian phonon scattering

The excitonic absorption spectrum for a disordered quantum well in presence of exciton-acoustic phonon interaction is treated beyond the Markov approximation. Realistic disorder exciton states are taken from a microscopic simulation, and the deformation potential interaction is implemented. The exciton Green's function is solved with a self energy in second order Born quality. The calculated spectra differ from a superposition of Lorentzian lineshapes by enhanced inter-peak absorption. This is a manifestation of pure dephasing which should be possible to measure in near-field experiments.Comment: 8 pages, 7 figure

Operator product expansions as a consequence of phase space properties

The paper presents a model-independent, nonperturbative proof of operator product expansions in quantum field theory. As an input, a recently proposed phase space condition is used that allows a precise description of point field structures. Based on the product expansions, we also define and analyze normal products (in the sense of Zimmermann).Comment: v3: minor wording changes, as to appear in J. Math. Phys.; 12 page

Comment on "Dephasing Times in Quantum Dots due to Elastic LO Phonon-Carrier Collisions"

This paper is a Comment on Phys. Rev. Lett. 85, 1516 (2000) by A.V. Uskov, A.-P. Jauho, B. Tromborg, J. Mork, and R. Lang.Comment: 1 page, 1 figure. Phys. Rev. Lett., accepte

Risikoschwangerschaft - iatrogene Risiken

Zusammenfassung: Zahlreiche Publikationen und Analysen zeigen, dass ein substantieller Teil von geburtshilflichen Fällen, bei denen Mutter oder Kind Schaden nehmen oder gar sterben, mit bedingt ist durch eine ungenügende medizinische Betreuung. Schwerwiegende mütterliche Fälle kommen mit einer Häufigkeit von etwa 5 auf 10.000 vor, jede 50. Frau stirbt daran. Bis zu 60% dieser Fälle sind assoziiert mit einer ungenügenden medizinischen Betreuung. Vergleichbare Ergebnisse sind für die kindliche Mortalität und Morbidität vorhanden. Mithilfe schriftlich festgelegter einheitlicher Prozesse und Verfahren, einer modernen Fehlerkultur, der Anwesenheit eines Facharztes rund um die Uhr und dem systematische Trainieren von Notsituationen (z.B. Schulterdystokie, atone Blutung, nicht geplante Sectio) könnte eine substantielle Zahl von iatrogen bedingten Zwischenfällen vermieden werde