Thermalization and Lyapunov Exponents in the Yang-Mills-Higgs Theory

We investigate thermalization processes occurring at different time scales in the Yang-Mills-Higgs system at high temperatures. We determine the largest Lyapunov exponent associated with the gauge fields and verify its relation to the perturbatively calculated damping rate of a static gauge boson.Comment: 33 pages (revtex), 4 PS figures, submitted to PR

Jet trails and Mach cones: The interaction of microquasars with the ISM

A sub-set of microquasars exhibit high peculiar velocity with respect to the local standard of rest due to the kicks they receive when being born in supernovae. The interaction between the radio plasma released by microquasar jets from such high-velocity binaries with the ISM must lead to the production of trails and bow shocks similar to what is observed in narrow-angle tailed radio galaxies and pulsar wind nebulae. We present a set of numerical simulations of this interaction that illuminate the long term dynamical evolution and the observational properties of these microquasar bow shock nebulae and trails. We find that this interaction always produces a structure that consists of a bow shock, a trailing neck, and an expanding bubble. Using our simulations to model emission, we predict that the shock surrounding the bubble and the neck should be visible in H{\alpha} emission, the interior of the bubble should be visible in synchrotron radio emission, and only the bow shock is likely to be detectable in X-ray emission. We construct an analytic model for the evolution of the neck and bubble shape and compare this model with observations of X-ray binary SAX J1712.6-3739.Comment: 33 pages, 13 figures, 1 table; Accepted to Ap

Klee sets and Chebyshev centers for the right Bregman distance

We systematically investigate the farthest distance function, farthest points, Klee sets, and Chebyshev centers, with respect to Bregman distances induced by Legendre functions. These objects are of considerable interest in Information Geometry and Machine Learning; when the Legendre function is specialized to the energy, one obtains classical notions from Approximation Theory and Convex Analysis. The contribution of this paper is twofold. First, we provide an affirmative answer to a recently-posed question on whether or not every Klee set with respect to the right Bregman distance is a singleton. Second, we prove uniqueness of the Chebyshev center and we present a characterization that relates to previous works by Garkavi, by Klee, and by Nielsen and Nock.Comment: 23 pages, 2 figures, 14 image

Adding low-dose antidepressants to interferon alpha treatment for chronic hepatitis C improved psychiatric tolerability in a patient with schizoaffective psychosis

Treatment of chronic hepatitis C with interferon alpha (IFN-alpha) is relatively contraindicated in patients with psychiatric disorders because of possible severe psychiatric side effects. We report on a case of a female patient with a chronic schizoaffective psychosis, who was treated for 3 months with 3 x 3 mio IE IFN-alpha s.c./week because of a chronic hepatitis C (genotype Ib). Psychosis was stable with flupentixol monotherapy. After 2 months, she developed a severe depressive syndrome which lead to suicidal ideation. Until this time, she was without any antidepressive medication. Depressive symptoms disappeared after interferon therapy was stopped. Under prophylactic treatment with low-dose trimipramine (50 mg) or nefazodone (200 mg/day) therapy with IFN-alpha 3 x 3 mio IE/week was re-established after several months and again 2 years later adding ribavirin 1200 mg/day, a virustaticum. In contrast to the symptoms during monotherapy with IFN-alpha, during the time of both combination treatments, no psychiatric side effects occurred. While for ribavirin antidepressant effects are not known, we suppose that antidepressants may in serotonergic or noradrenergic caused by IFN-alpha. prevent changes neurotransmission caused by IFN-alpha. Copyright (C) 2000 S. Karger AG, Basel

Resonance contributions to HBT correlation radii

We study the effect of resonance decays on intensity interferometry for heavy ion collisions. Collective expansion of the source leads to a dependence of the two-particle correlation function on the pair momentum K. This opens the possibility to reconstruct the dynamics of the source from the K-dependence of the measured HBT radii. Here we address the question to what extent resonance decays can fake such a flow signal. Within a simple parametrization for the emission function we present a comprehensive analysis of the interplay of flow and resonance decays on the one- and two-particle spectra. We discuss in detail the non-Gaussian features of the correlation function introduced by long-lived resonances and the resulting problems in extracting meaningful HBT radii. We propose to define them in terms of the second order q-moments of the correlator C(q, K). We show that this yields a more reliable characterisation of the correlator in terms of its width and the correlation strength `lambda' than other commonly used fit procedures. The normalized fourth-order q-moments (kurtosis) provide a quantitative measure for the non-Gaussian features of the correlator. At least for the class of models studied here, the kurtosis helps separating effects from expansion flow and resonance decays, and provides the cleanest signal to distinguish between scenarios with and without transverse flow.Comment: 23 pages, twocolumn RevTeX, 12 eps-figures included, minor changes following referee comment

Hydrodynamic emission of strange and non-strange particles at RHIC and LHC

The hydrodynamic model is used to describe the single-particle spectra and elliptic flow of hadrons at RHIC and to predict the emission angle dependence of HBT correlations at RHIC and LHC energies.Comment: 6 pages LaTeX, 3 postscript figures. Proceedings for the conference "Strange Quark Matter 2003", Atlantic Beach, NC, March 12-17, 2003, to appear in J. Phys.

Lattice Gauge Description of Colliding Nuclei

We propose a novel formalism for simultaneously describing both, the hard and soft parton dynamics in ultrarelativistic collisions of nuclei. The emission of gluons from the initially coherent parton configurations of the colliding nuclei and low-$p_t$ color coherence effects are treated in the framework of a Yang-Mills transport equation on a coupled lattice-particle system. A collision term is added to the transport equation to account for the remaining intermediate and high-$p_t$ interactions in an infrared finite manner.Comment: 8 page

Systematic study of the jet fragmentation function for inclusive jet-production in p+p collisions at sqrt{s}=200 GeV in STAR

Jet fragmentation functions measured in e^+e^- and p+\bar{p} experiments are well-described on an inclusive hadron level by QCD-based calculations. Fragmentation is expected to be modified by the presence of a strongly interacting medium, but full theoretical description of this modification must still be developed. It has recently been suggested that particle-identified fragmentation functions may provide additional insight into the processes underlying jet quenching. To assess the applicability of QCD-based fragmentation calculations to RHIC data, and to provide a baseline with which to compare fragmentation function measurements in heavy ion collisions, we present the first measurements of charged hadron and particle-identified fragmentation functions of jets reconstructed via a midpoint-cone algorithm from p+p collisions at 200 GeV in STAR. We study the dependence on jet cone-size and jet-energy, and compare the results to PYTHIA simulations based on the Modified Leading Log Approximation (MLLA).Comment: 6 pages, 5 figures, proceedings of Hard Probes 2008 conferenc

Teachers’ Beliefs Concerning Teaching Multilingual Learners: A Cross-Cultural Comparison Between the US and Germany

We analysed the beliefs about multilingualism in school of in-service teachers from the US (n = 60) and Germany (n = 65), utilising a survey originally developed in German that was translated and adapted into English. Results show that teachers from both samples, on average, strongly agree that a person’s identity is connected to their language and culture. However, we found significant differences in scale mean values between US teachers and German teachers concerning their beliefs about (1) the interconnected nature of language with culture and identity, (2) language demand in content classrooms, (3) responsibility for language teaching, and (4) valuing multilingualism. Our results provide insight into cross-cultural differences between German and US teachers’ beliefs, as well as a strong instrument in two languages to measure teachers’ beliefs about multilingualism in schools