On the efficient numerical solution of lattice systems with low-order couplings

We apply the Quasi Monte Carlo (QMC) and recursive numerical integration methods to evaluate the Euclidean, discretized time path-integral for the quantum mechanical anharmonic oscillator and a topological quantum mechanical rotor model. For the anharmonic oscillator both methods outperform standard Markov Chain Monte Carlo methods and show a significantly improved error scaling. For the quantum mechanical rotor we could, however, not find a successful way employing QMC. On the other hand, the recursive numerical integration method works extremely well for this model and shows an at least exponentially fast error scaling

Tests of isospin symmetry breaking at ϕ(1020)\phi (1020) meson factories

In a model of isospin symmetry breaking we obtain the ($e^{-} e^{+} \rightarrow \pi^{-} \pi^{+}$) amplitude $Q$ and the isospin $I=0$ and $I=1$ relative phase $\psi$ at the $\phi (1020)$ resonance in aproximate agreement with experiment. The model predicts \Gamma(\phi \rightarrow \omega \pi^{0}) \approx 4 \cdot 10^{-4} \;\mbox{MeV}. We have also obtained \Gamma (\phi \rightarrow \eta' \gamma)=5.2 \cdot 10^{-4} \;\mbox{MeV}. Measuring this partial width would strongly constrain $\eta$-$\eta'$ mixing. The branching ratios $BR$ of the isospin violating decays $\rho^{+} \rightarrow \pi^{+} \eta$ and $\eta' \rightarrow \rho^{\pm} \pi^{\mp}$ are predicted to be $BR(\rho^{+} \rightarrow \pi^{+} \eta)=3 \cdot 10^{-5}$ and $BR(\eta' \rightarrow \rho^{\pm} \pi^{\mp})=4 \cdot 10^{-3}$, respectively, leading to $BR[\phi \rightarrow \rho^{\pm} \pi^{\mp} \rightarrow (\pi^{\pm} \eta)\pi^{\mp} \rightarrow (\pi^{\pm} \gamma \gamma)\pi^{\mp}]=10^{-6}$ and $BR[\phi \rightarrow \eta' \gamma \rightarrow (\rho^{\pm} \pi^{\mp})\gamma]=2\cdot 10^{-6}$.Comment: 11 pages 2 Figures ( not included available on request ), Latex, Karlsruhe TTP42-9

Orbital electron capture by the nucleus

The theory of nuclear electron capture is reviewed in the light of current understanding of weak interactions. Experimental methods and results regarding capture probabilities, capture ratios, and EC/Beta(+) ratios are summarized. Radiative electron capture is discussed, including both theory and experiment. Atomic wave function overlap and electron exchange effects are covered, as are atomic transitions that accompany nuclear electron capture. Tables are provided to assist the reader in determining quantities of interest for specific cases

High-Dimensional Stochastic Design Optimization by Adaptive-Sparse Polynomial Dimensional Decomposition

This paper presents a novel adaptive-sparse polynomial dimensional decomposition (PDD) method for stochastic design optimization of complex systems. The method entails an adaptive-sparse PDD approximation of a high-dimensional stochastic response for statistical moment and reliability analyses; a novel integration of the adaptive-sparse PDD approximation and score functions for estimating the first-order design sensitivities of the statistical moments and failure probability; and standard gradient-based optimization algorithms. New analytical formulae are presented for the design sensitivities that are simultaneously determined along with the moments or the failure probability. Numerical results stemming from mathematical functions indicate that the new method provides more computationally efficient design solutions than the existing methods. Finally, stochastic shape optimization of a jet engine bracket with 79 variables was performed, demonstrating the power of the new method to tackle practical engineering problems.Comment: 18 pages, 2 figures, to appear in Sparse Grids and Applications--Stuttgart 2014, Lecture Notes in Computational Science and Engineering 109, edited by J. Garcke and D. Pfl\"{u}ger, Springer International Publishing, 201

Bayesian Analysis of the Polarization of Distant Radio Sources: Limits on Cosmological Birefringence

A recent study of the rotation of the plane of polarization of light from 160 cosmological sources claims to find significant evidence for cosmological anisotropy. We point out methodological weaknesses of that study, and reanalyze the same data using Bayesian methods that overcome these problems. We find that the data always favor isotropic models for the distribution of observed polarizations over counterparts that have a cosmological anisotropy of the type advocated in the earlier study. Although anisotropic models are not completely ruled out, the data put strong lower limits on the length scale $\lambda$ (in units of the Hubble length) associated with the anisotropy; the lower limits of 95% credible regions for $\lambda$ lie between 0.43 and 0.62 in all anisotropic models we studied, values several times larger than the best-fit value of $\lambda \approx 0.1$ found in the earlier study. The length scale is not constrained from above. The vast majority of sources in the data are at distances closer than 0.4 Hubble lengths (corresponding to a redshift of $\approx$0.8); the results are thus consistent with there being no significant anisotropy on the length scale probed by these data.Comment: 8 pages, 3 figures; submitted to Phys. Rev.

Die Ge-Komposita im Mittelhochdeutschen : Eine zur Zeit noch bestehende Möglichkeit, eine Aussage aspektuell zu markieren

Ge- signale l’absence de tout caractère actualisant, de toute actualité dans un temps particulier, signale la discongruence à l’actualisation une et particulière (LSL, 65, note15). On comprend pourquoi le sens absolu de la négation nie "jamais” a tant d’affinité avec le composé. Cette prédication (structure d\u27affirmation en ge-)  fait “l’économie de l’épreuve et de la réduction du singulier” pour entrer de plain-pied dans l’universel (Levinas). Das getue ich niemer mêre : Cette prédication est d’emblée installée non pas “en un moment quelconque du temps”, comme le formule Maurice Marache, mais plutôt dans ce que F. W. J. Schelling appelle l’éternité, ce temps virtuel qui ne cesse de donner du temps sans jamais s’épuiser, dans le temps en réserve d’actualisations. Ge- serait un aspect “anti-détensif, qui bloquerait, empêcherait toute détension du verbe, toute descente vers une incarnation du processus dans le réel. (cf. Daviet-Taylor, HEL, 1993).

Strangeness in the Nucleon: The Strange Vector Form Factors

We discuss two descriptions of the nucleon's strange vector form factors in the framework of vector meson dominance. The first, an updated and extended version of Jaffe's dispersion analysis, approximates the spectral functions of the form factors as a sum of vector meson poles, whereas the second combines vector meson dominance in the $\omega$ and $\phi$ meson sector with an intrinsic strangeness distribution from a kaon cloud. (Plenary talk given at the International School for Nuclear Physics, 17th Course: Quarks and Hadrons in Nuclei, Erice, Sicily, Sept 19-27, 1995.)Comment: 12 pages (LaTeX), 2 postscript figures, to appear in Prog. Part. Nucl. Phys. 36 (1996

Latest Developments from the S-DALINAC*

The S-DALINAC is a 130 MeV superconducting recirculating electron accelerator serving several nuclear and radiation physics experiments as well as driving an infrared free-electron laser. A system of normal conducting rf resonators for noninvasive beam position and current measurement was established. For the measurement of gamma-radiation inside the accelerator cave a system of Compton diodes has been developed and tested. Detailed investigations of the transverse phasespace were carried out with a tomographical reconstruction method of optical transition radiation spots. The method can be applied also to non-Gaussian phasespace distributions. The results are in good accordance with simulations. To improve the quality factor of the superconducting 3 GHz cavities, an external 2K testcryostat was commissioned. The influence of electro-chemical polishing and magnetic shielding is currently under investigation. A digital rf-feedback-system for the accelerator cavities is being developed in order to improve the energy spread of the beam of the S-DALINAC. * Supported by the BMBF under contract no. 06 DA 820, the DFG under contract no. Ri 242/12-1 and -2 and the DFG Graduiertenkolleg 'Physik und Technik von Beschleunigern